Using deep gravel and bacteria to control nitrogen

[dw1305]

Hi all,

What I find interesting about all this is how the various bacteria etc. in the bio-film are located at specific depths and juxtapositions. They are arrayed in such a fashion that they get what they need. And the work together, the same bacteria that would break down organic waste will break down the dead bacteria in the bio-film turning to something other bacteria can use and vice versa. Moreover, the bio-film also affords them protection from all sorts of "bad" things including drying out.

Thank you very much for the links, I've downloaded them and I'll be very interested in having a proper look through them. I'm still hoping that we will do more "waste water" work in the future.

cheers Darrel

[David R]

I'll start with a little disclaimer that I have only very lightly skim-read the rather lengthy and detailed replies in this thread, but here's my 2c...

I wouldn't even consider the idea of using a deep substrate bed for this purpose in a FW aquarium for many reasons, but mainly because it wastes valuable swimming space and almost certainly won't be as effective as using terrestrial plants with submerged roots, such as Pothos (Epipremnum aureum), to keep nitrates in check. I have two plants growing in the sump of my 2000L tank, and with my moderate stocking even feeding 2-3 times daily I rarely hit 10ppm a week after a water change. I could get away with changing <10% weekly based on nitrate readings alone (or much longer intervals between changes), but I still usually change 20-30% weekly for all the other factors not tested for. It is nice to know I have the capacity to go away for a couple of weeks without having to worry about someone else doing a water change on the tank though.

If you are trying to extend the period between water changes I'd say Pothos are a must, they don't need much light (mine are under an 8W compact fluorescent bulb in a desk lamp) and they don't require CO2 during the day, or release it back into the water at night, like submerged plants. They're easy to find almost anywhere house plants are sold, often called 'Devils Ivy' or 'Golden Pothos'.

[bekateen]

Hi David,
Thanks for the suggestions.

I wouldn't even consider the idea of using a deep substrate bed for this purpose in a FW aquarium for many reasons, but mainly because it wastes valuable swimming space

Very true - As I mentioned above, I set up an experimental tank, a standard 15 Gallon, with 4" gravel and dang it looks silly - the gravel occupies approximately 40% of the depth of the tank. LOL - Definitely not desirable in shallower tanks, although I would think not so significant in taller tanks (my 36 Gallon bowfront already has almost 3" of sand in the bottom, and I think it looks pretty good; one more inch wouldn't be too severe in that tank). And your concern about depth and swimming space is something I ponder - One of the resources sited in an earlier post in this thread stated that the anaerobic denitrifying bacteria exist in the 3-4" depth range; if so, then maybe I can get away with slightly less substrate than a full 4".

... Pothos (Epipremnum aureum)... I have two plants growing in the sump of my 2000L tank... If you are trying to extend the period between water changes I'd say Pothos are a must.

Compared to how you described your tank, I think I have a heavier nitrogen-load (per gallon) in my main tank, between the number of fish and the amount of food I give them (plus, since I maintain a live colony of Tubifex worms in the sandy substrate for the cats to graze on ad libidum, these worms are not only excess food for fish but they are simultaneously animals contributing to the nitrogen waste in the tank).

My tank is planted, but I've never tried what you're suggesting. On this point, I have to be honest about my naïveté: I have no experience with sumps. I have used Golden Pothos before in semi-aquatic terraria set up for my frogs (at home, not work), but can it be used in a fully aquatic setting? Doesn't it have to be at least partially aerial? If so, that would be a challenge for me because my tanks have only a very small air space above the water (a couple of inches between the water level and the standard manufacturer's hood. All the plants-on-top aquaria I've ever seen are open-topped, but my tanks aren't. If I can work around that limitation, your idea is very appealing to me; I'd enjoy having plants grow above the water line.

I'll try and tinker around with this some.
Cheers, Eric

[dw1305]

Hi all,

I have used Golden Pothos before in semi-aquatic terraria set up for my frogs (at home, not work), but can it be used in a fully aquatic setting? Doesn't it have to be at least partially aerial?

The Pothos (Epipremnum aureum) just has the lower end of the stem in the water, the leaves are all emersed.

If you haven't got much space between the lid and the water you can use floaters, or let an Anubias grow out above the water level. These are Hygrophila corymbosa and Anubias barteri that have "escaped".



cheers Darrel

[bekateen]

Yes, I can definitely do that! It's always been my understanding that terrestrial plants can be more photosynthetic because of the direct light exposure (no light being absorbed by water). Does this small portion of plant above the waterline really have a bigger impact on nitrate levels than a proportional amount of submerged plant?

And as for floaters, I used to have duckweed on the surface of one of my tanks, but it was all tussled about by my overactive external power filter, eventually getting sucked in and clogging the filter, and ultimately getting destroyed by the filter. What about the various pond lilies sold in pet shops: Do they grow too large for aquaria?

As an aside, the LFS owner advocating deep gravel also uses duckweed and floating plants; bases on my problem with my duckweed, I suspect that's one reason why he advocates weaker filtration rather than overfiltration. He also uses a really neat trick tying mosses and other small rootless plants to vertical styrofoam sheets partially submerged at the back of the tank. This creates a wall of greenery, some of the blocks sticking out of the water an inch or two. And for these he creates a gentle water return above the plants to keep them wet. When the plants overgrow the foam, it looks really cool, and I'm sure it helps a lot with nitrates too.

[dw1305]

Hi all,

It's always been my understanding that terrestrial plants can be more photosynthetic because of the direct light exposure (no light being absorbed by water). Does this small portion of plant above the waterline really have a bigger impact on nitrate levels than a proportional amount of submerged plant?

That would be true in lakes etc. but I think in the shallow, relatively transparent, water we have in out tanks that CO2 availability is a much bigger issue. Emergent plants have access to ~400ppm CO2 as against ~2ppm in submerged conditions. Light drives photosynthesis, but carbon availability is often the limiting factor. I haven't got any figures but emergent plants definitely help with nutrient removal.

This is why aquascapers aim for ~30ppm CO2, even higher levels would be optimal for plants, but you asphyxiate your live stock via the Bohr Root effect. They also add unlimited nutrients via "Estimative Index" and achieve startling plant growth.

I'm not interested in optimal plant growth, I'm interested in the plants maintaining high water quality.

And as for floaters, I used to have duckweed on the surface of one of my tanks, but it was all tussled about by my overactive external power filter, eventually getting sucked in and clogging the filter, and ultimately getting destroyed by the filter. What about the various pond lilies sold in pet shops: Do they grow too large for aquaria?

I have Frogbit, Nile Cabbage and Salvinia, and as you can see from the picture I have reasonable surface flow, but a big sponge on the filter. You can get Lilies for the aquarium, they grow a bit big generally, but you can control them by removing some of the floating pads. I have had Nymphaea lotus 'Red' in a 2' tank for the last ~5 years, and I only let it have 3 floating leaves. If I go away for a couple of weeks it will have covered the surface by the time I'm back.

As an aside, the LFS owner advocating deep gravel also uses duckweed and floating plants; bases on my problem with my duckweed, I suspect that's one reason why he advocates weaker filtration rather than overfiltration. He also uses a really neat trick tying mosses and other small rootless plants to vertical styrofoam sheets partially submerged at the back of the tank. This creates a wall of greenery, some of the blocks sticking out of the water an inch or two. And for these he creates a gentle water return above the plants to keep them wet. When the plants overgrow the foam, it looks really cool, and I'm sure it helps a lot with nitrates too.

I'd recommend this approach. I don't think it really matters whether your LFS changes much water etc. he has a set up which is pretty robust and stable in terms of water quality. Whether the deep gravel bed out-gases much N2 is pretty well irrelevant, the tank set-up will maintain water quality.

cheers Darrel

[bekateen]

Just a quick reply, because I'm on my mobile phone. Of course, the CO2, duh! Don't know why I didn't think that in first place.

Don't find many floating plants at LFS in Stockton (IDK why not). Yesterday I drove 1 hour to LFS in Sacramento to get some frogbit and a few other rooted plants. IMHO, that's a long way to drive for plants - I think I just crossed the line into "aquarium freak."

By the way, what is "floating Anubius?" Is it just normal Anubius that isn't planted in the substrate, or is it a special type of Anubius?

Yes it's all about finding that balance. Hopefully I find it sooner than later.
Thanks, Eric

[dw1305]

Hi all,

By the way, what is "floating Anubius?" Is it just normal Anubius that isn't planted in the substrate

Yes it is just a normal Anubias. I used to have them all fixed to pieces of bog-wood etc., but now I just chunk a bit off and put it in the tank and ignore it. If I have a new tank I would re-attach them to some wood, but most of my tanks are pretty full of plants so I don't really need to, I can just put them in.

Don't find many floating plants at LFS in Stockton

No they aren't off for sale in UK ones either. I'm not sure why this is. Possibly because Tropica etc grew most of their plants emersed? or possibly because they don't sell?

I give as many of my spares away as possible to hobbiests and a local LFS, but I always have spare.

cheers Darrel

[Raul-7]

As far as floating plants, the best for nitrates are Eichornia sp.; they are commonly used in waste water treatment. http://article.sapub.org/10.5923.j.re.2 ... tml#Sec3.1

As far as emerged, I'd say Pothos works really well.


Or you can setup a reactor using a media like Sachem deNitrate and run a low flow pump [less than 50gph] through it to cultivate anaerobic bacteria to convert that NO3 into N2.

[bekateen]

As far as floating plants, the best for nitrates are Eichornia sp.; they are commonly used in waste water treatment. http://article.sapub.org/10.5923.j.re.2 ... tml#Sec3.1

As far as emerged, I'd say Pothos works really well.


Or you can setup a reactor using a media like Sachem deNitrate and run a low flow pump [less than 50gph] through it to cultivate anaerobic bacteria to convert that NO3 into N2.

Thanks Raul-7. Hyacinth are beautiful plants, too. I'll see what's available in my area.
Eric

[dw1305]

Hi all,
"Raul7" you are right, but I'd only recommend Eichornia if you have a lot of light. I've tried it a few times, but it always dwindles away in the winter. You may have more joy in California, we are a long way N. in the UK, and our winters are pretty gloomy.

Pistia is almost as good, and is more tolerant of lower light. If you look at the posted link (by Raul7) the details for Pistia are immediately after those for Eichornia.

An alternative route, using anoxic denitrification of NO3 and out gassing as N2, is described in "twotankamin's" very informative posts and links earlier in the thread.

cheers Darrel

[pleco_breeder]

Just a quick note. Water hyacinth are considered invasive, and illegal to sell, purchase, or transport in California. This holds true for most states within the US as well. I don't know the disposal method used in California, but know having one found in your tanks or ponds in Arizona results in the water being "bombed" with a strong herbicide to remove any risk of seeds within the system. It's probably not worth the risk when other methods can work.

EDIT: I hadn't reviewed the page fully before posting, but feel I would be remiss if I didn't mention that Pistia is also controlled in a lot of areas. I don't think this currently includes California, but definitely check on it before taking the risk.

Larry

[dw1305]

Hi all,

Water hyacinth are considered invasive, and illegal to sell, purchase, or transport in California

That is a good point, it is one of the world's worst weeds. I'm not knowledgeable about US laws, but I should probably have thought of that: Eichornia crassipes via UF/IFAS Center for Aquatic and Invasive Plants <http://plants.ifas.ufl.edu/node/141>.

From the same site Pistia may, or may not, be native to the USA, and isn't on the list of Federal noxious weeds <http://plants.ifas.ufl.edu/node/328>.

cheers Darrel

[bekateen]

Just a quick note. Water hyacinth are considered invasive, and illegal to sell, purchase, or transport in California. This holds true for most states within the US as well. I don't know the disposal method used in California, but know having one found in your tanks or ponds in Arizona results in the water being "bombed" with a strong herbicide to remove any risk of seeds within the system. It's probably not worth the risk when other methods can work.

EDIT: I hadn't reviewed the page fully before posting, but feel I would be remiss if I didn't mention that Pistia is also controlled in a lot of areas. I don't think this currently includes California, but definitely check on it before taking the risk.

Larry

Definitely, thank you Larry.
Eric

[TwoTankAmin]

I forgot about this study, it shows how a planted substrate with roots differs from those not planted. here is a link to the full paper:

Nitrification and denitrification in the rhizosphere of the aquatic macrophyte
Lobelia dortmanna L.
Nils Risgaard-Petersen and Kim Jensen
Institute of Biological Science, Department of Microbial Ecology, University of Aarhus, Ny Munkegade Bldg. 540,
DK-8000 Aarhus C, Denmark

Abstract
Nitrogen and 0, transformations were studied in sediments covered by Lobelia dortmanna L.; a combination of
lsN isotope pairing and microsensor (0,, NO,-, and NH,+) techniques were used. Transformation rates and microprofiles
were compared with data obtained in bare sediments. The two types of sediment were incubated in doublecompartment
chambers connected to a continuous flow-through system.
The presence of L. dortmanna profoundly influenced both the nitrification-denitrification activity and porewater
profiles of 02, NO,-, and NH,+ within the sediment. The rate of coupled nitrification-denitrification was greater
than sixfold higher in L. dortmanna-vegetated sediment than in bare sediment throughout the light-dark cycle.
Illumination of the Lobelia sediment reduced denitrification activity by -30%. In contrast, this process was unaffected
by light-dark shifts in the bare sediment. Oxygen microprofiles showed that 0, was released from the L.
dortmanna roots to the surrounding sediment both during illumination and in darkness. This release of 0, expanded
the oxic sediment volume and stimulated nitrification, shown by the high concentrations of NO,- (-30 FM) that
accumulated within the rhizosphere. Both lsN, isotope and microsensor data showed that the root-associated nitrification
site was surrounded by two sites of denitrification above and below, and this led to a more efficient coupling
between nitrification and denitrification in the Lobelia sediment than in the bare sediment.

fromhttp://m.m.aslo.info/lo/toc/vol_42/issue_3/0529.pdf

The paper was investigating why a plant would transport oxygen via its roots such that the result would be to foster nitrifying and denitrifying bacteria which would be in competition for nitrogen with the plant- ammonia (as NH4) and nitrate. For this discussion the relevant thing to take from this paper here are that nitrification coupled with denitrification is natures way. And it seems to me this would be perfectly fine in a tank. After all aren't filters basically intended to do as much of the job nature does as is possible?

I do not see how having both nitrifying and denitrifying bacteria coexisting in an established fw tank or that their presence in the same filter in such a tank is anything but beneficial from the research I have read. Nor can one really argue that the removal of some free O from the water going through the media in a filter by bacteria, especially in a planted tank, is a danger. Considering how much oxygen fish breath and that plants use at night, this would surely deplete DO levels a lot more than anything bacteria might do. If this were an issue, there would be a whole lot more suffocated dead fish in tanks all over the world.

However, I am open minded and am willing to consider any science which shows the above to be incorrect. I welcome reading any links to the science which shows having both nitrifying and denitrifying bacteria at work in a tank, be it in the substrate or in the the filter, is a bad or unnatural thing. (I specifically mean having them living in close proximity as in the same media, bio-film or planted substrate.) I learn as much by being shown I am wrong as I do from being shown what is right.

[bekateen]

TwoTankAmin, thanks for the reference. I'm swamped at work for the next few days, but I'll read the full article as soon as I can. The more perspective, the better!
Cheers,
Eric

[dw1305]

Hi all,

The paper was investigating why a plant would transport oxygen via its roots such that the result would be to foster nitrifying and denitrifying bacteria which would be in competition for nitrogen with the plant- ammonia (as NH4) and nitrate. For this discussion the relevant thing to take from this paper here are that nitrification coupled with denitrification is natures way. And it seems to me this would be perfectly fine in a tank. After all aren't filters basically intended to do as much of the job nature does as is possible? I do not see how having both nitrifying and denitrifying bacteria coexisting in an established fw tank or that their presence in the same filter in such a tank is anything but beneficial from the research I have read.

I don't think any-one is arguing that de-nitrification isn't a good thing in the substrate, but I'm convinced it can rapidly become a problem in the filter media.

This is because you have both aerobic and anaerobic processes occurring with little spatial separation. You need to obtain a balance where have a steep oxygen gradient from aerobic to anaerobic over a very short distance

The conversion of NH3 to NO2 to NO3 is an oxygen intensive process (we've gone from 3 hydrogen atoms to 3 oxygen), and we are much more concerned with NH3 & NO2 than we are with NO3.

Ammonia and nitrite are toxic at very low levels, whilst NO3 has very low toxicity. I don't care if NO3 levels rise, the plants in the tank will respond with extra growth, but if NO2 or NH3 levels rise I'd have dead fish long before the plants have depleted the extra nitrogen.

The problem with de-nitrification occurring in the filter media
If the bio-load increases (extra ammonia from a decaying fish, emergency chloramine dosing in the tap water, etc.) or the supply of oxygen falls (partially blocked filter, very low atmospheric pressure, very warm water etc) you have a situation where the water in the filter will rapidly become de-oxygenated and ammonia will build up, starting a positive feed-back loop of lower oxygen, more ammonia, fish death, leading to more ammonia, lower oxygen levels etc.

Why aerobic filter media has built in stability
If you keep all the filter media aerobic you have much more capacity to deal with the scenarios above, as long as we can keep a flow of oxygenated water across the filter media it has an enormous capacity to deal with increased bio-load. This is why sewage works use "wet and dry" trickle filter beds, the large gas exchange surface allows the beds to deal with "water" with a huge bio-load.

Why having a relatively undisturbed substrate and plants will improve water quality
I keep planted tanks, with a substrate and emergent plants, for exactly the reasons set out in the Lobelia dortmanna study. I don't vacuum my substrate, or re-plant the plants, and fairly quickly after planting the substrate will have zones of positive and negative REDOX activity.

Within the upper substrate you will get aerobic nitrification, but only a few centimetres below the substrates’ surface as oxygen levels you get a zone of "facultative anaerobes" they utilise oxygen when it is available, but if O2 levels are low, they use NO3, stripping the oxygen and out-gassing (N2) gas.

In the substrate you are in system like you are suggesting for the filter, with the aerobic nitrifying bacteria providing the nitrate, and their high oxygen demand using the limited supply of oxygen.

The real difference is that the very upper zone of the substrate, and the immediate plant rhizosphere, will always being oxygenated. At the tank water substrate boundary you have a much more extensive gas exchange surface, which is immediately below a water column which is in contact with atmospheric oxygen levels.

I'm always go to have plants and a substrate and I'm going to leave the substrate relatively undisturbed.

cheers Darrel

[dw1305]

Hi all,
I should also have said the closest analogy to keeping tanks for Loricariids would be from commercial aquaculture of Salmonids, using re-circulating systems. The advantage that examples from Salmonid culture over waste water treatment, or aquaculture systems for Channel Catfish or Tilapia, is that Salmonids are a lot less forgiving of lapses in water quality and require high levels of oxygenation at all times.

This is: Neil et al. (2013) "Freshwater Culture Of Salmonids In Recirculating Aquaculture Systems (RAS) With Emphasis On The Monitoring And Control Of Key Environmental Parameters." University of Glasgow <http://eprints.gla.ac.uk/85116/1/85116.pdf>.

This is a review of of "Hybrid constructed wetlands for wastewater treatment" <http://www.iaees.org/publications/journ ... atment.pdf>. In these systems there would be both aerobic nitrification and anaerobic de-nitrification, but with a spatial separation between them.

cheers Darrel

[TwoTankAmin]

I guess I am failing to explain the processes and bacteria involved clearly. So I will lean on SeaCgem to do it. They have a nedia called Matrix which is specifically designed to foster and support nitrification and denitrification in a single filter in the same media.

Matrix™ is a high porosity biomedia that provides efficient biofiltration for the removal of nitrogenous waste. Matrix™ is a porous inorganic solid about 10 mm in diameter. Each liter of Matrix™ provides as much surface (>~700 m2) as 170 liters of plastic balls! Plastic bio-materials provide only external surface area, whereas Matrix™ provides both external and internal macroporous surface area. These macropores are ideally sized for the support of nitrifying and denitrifying bacteria. This allows Matrix™, unlike other forms of biomedia, to remove nitrate along with ammonia and nitrite, simultaneously and in the same filter.

Matrix™ is completely inert and will not breakdown. It need not be replaced. Since the majority of the bacteria are internal, Matrix™ may be rinsed when needed without damaging the filter. Matrix™ is compatible with all types of wet or wet-dry filters.........

For biological filter media, specific surface area (measured as surface area per gram of material, or surface area per some specified volume of material) is very important. These products provide surface sites for bacteria to attach and do their work. The greater the surface area per gram of medium, the greater the number of bacteria that can attach. Thus a high specific surface area is desirable.

There is a second consideration, and that is the size of the pores in the medium. Generally, with very large pore diameters, we have smaller specific surface area, so that is not good. This generally rules out pores above 10 microns in diameter. But we can go too far in the other direction. If we have a very large number of very, very small pores, then our specific surface area number will be phenomenal, but the medium will not work very well as a biological medium. This is due to physical limitations, specifically too small a volume to support bacterial growth, and the decreasing efficiency of fluid transport (necessary to carry nutrients to the bacteria and waste away from the bacteria) with very small pore sizes. (Small pores still play important roles in physical and chemical processes, such as adsorption.)

from http://www.seachem.com/Products/product ... atrix.html

But let me come at this from another angle, Oxygen. The bacteria that do the denitrification are the facultative aerobes. Moreover, they get there originally because there is oxygen for them in the tank water. As long as they are not "forced" into denitrification, they are using up oxygen. Over time as a biofilm matures, it becomes possible for the autotrophic and heterotrophic aerobes to use all the O that comes their way and the result is that there is now nitrate but no free O left at that given depth of the biofim. And this will be the case whether or not there are any denitrifiers present. So inside the biofilm deeper in the media, the facultative bacteria living there will not get any free O. But instead of dying off to be in balance with the available O for them, they are able to switch over to using nitrate. When they do this they are no longer using free O. since it has been used up by the other bacteria. However, now they are denitrifying the tank, which is a benefit. So, bacteria that were using free O stop doing so and nitrate which was accumulating is now being reduced.

This all becomes much more relevant in those millions of tanks which have no plants and/or no substrate. It is fine to say "I do only planted tanks." unfortunately that is of little help to all those tanks with no or minimal plants. "Help, I have 40 ppm nitrate in my tap water and I keep an overstocked African rift lake tank for Tangs. How can I deal with high nitrate?"

I still see no logical nor scientific reason for not having nitrification and denitrification inside the same media and filter on a freshwater tank. Now if somebody has a greater than normal nitrate problem, I can see setting up a second filter with even better media for denitrification such as biodegrading polymer beads. But even this method requires the initial colonization of the biofilm by aerobes which will deplete the O for the denitrifiers to work.

Finally, at its heart the purpose of filtration in an aquarium is to do the work nature would in the wild. The ideal tank would be one in which we never changed the water and the filter and/or planting took care of the water quality. The ideal tank would be a self sustaining ecosystem. Now we all know this is impossible. However, I think it makes sense to get as close to this ideal state as we can, biologically speaking. Denitrifying bacteria should potentially be a better way to deal with excess nitrate than water changes or chemicals just as ammonia oxidizing microorganisms are a better way to deal with ammonia than water changes or chemicals.

[dw1305]

Hi all,

So inside the biofilm deeper in the media, the facultative bacteria living there will not get any free O. But instead of dying off to be in balance with the available O for them, they are able to switch over to using nitrate. When they do this they are no longer using free O. since it has been used up by the other bacteria. However, now they are denitrifying the tank, which is a benefit. So, bacteria that were using free O stop doing so and nitrate which was accumulating is now being reduced.

I think we will just have to differ on whether denitrification in the filter material is a good idea. I'm not saying it isn't possible, because it obviously is, but I'm really interested in the probable, rather than the possible.

Risk management, negative feedback and single point of failure
I'm going to talk about "single point of failure", resilience and risk assessment. They are fairly prosaic titles, and it isn't going to be a very exciting, but I would recommend it as an approach to everybody.

Single point of failure

This all becomes much more relevant in those millions of tanks which have no plants and/or no substrate. It is fine to say "I do only planted tanks." unfortunately that is of little help to all those tanks with no or minimal plants. "Help, I have 40 ppm nitrate in my tap water and I keep an overstocked African rift lake tank for Tangs. How can I deal with high nitrate?"

Problems with this is the filter has now become a "single point of failure".

It is also a severe risk and has a reasonable likelihood of happening.

If I was in this position, I would want the "no substrate, no plants" scenario to occur for as short a time as possible. As soon as I could I would add a substrate, even a thin layer of sand. I've now added resilience (I'm still dependent upon the filter, but I have a secondary site for nitrification in the substrate). If I add plants (they can be planted in a separate tank, or in planting basket with their stems emergent, or in an over-tank trickle filter) I've added more resilience, and also a negative feedback loop and an indication of the nutrient status of the tank (via the Duckweed Index <http://www.planetcatfish.com/forum/view ... weed+index>).

Tank design and management based upon risk assessment
It's not a "sexy" subject, but I'll cover it anyway.

My primary concern, and the primary requirement of all fish is that the water has enough dissolved oxygen at all times. If we have even a very limited period where the water doesn't have enough oxygen for the fishes requirement, the fish will die. Oxygen requirement will differ between fish, but large rheophilic fish are particularly at risk, which is partially why I wrote "Aeration and dissolved oxygen in the aquarium" <http://plecoplanet.com/?page_id=829>, this covers the mechanisms that deplete, and replenish, oxygen in the aquarium. As well as tank dimensions, and methods of adding oxygen to the water and removing CO2 etc., it has quite a lot on biological filtration because that is one of the major users of dissolved oxygen.

Because low oxygen levels are a severe risk I need to minimise the chances of them occurring, which is why I don't want potential single points of failure, or systems which require continual maintenance to keep them functioning. High NO3 levels are a low risk to the fish, but high NH3 levels will kill them by both direct toxicity and by depleting the available dissolved oxygen.

I want stable resilient systems, where if things go wrong I have secondary systems (an additional filter etc.) and negative feedback loops ("belt and braces") to keep the fish alive, and buy me enough time to make the necessary changes.

cheers Darrel

[JamesFish]

As this is no longer strictly a gravel based discussion anymore I will chime in with a little run I have had using the JBL BioNitratex media. Its practical for me due to low water volume. At £20 a box for 4 packets. Each packet is capable of doing 50L at a stocking level of 1cm per 5L of water. I suspect I am over so my packets will burn out early. They have a max life of 1 year.

Huge water changes early on as I was close or above the 50ppm that is the max level the packets tolerated. Than as the last packet was added slowly reduced each week to not shock the fish.

Overall result on basic test kits are lower TDS by about 100. PH down 0.8 from 8 to 7.2 . Nothing to drastic do wonder what the solids are that have disappeared? - Nitrates however have dropped to the lowest in all setups. I rarely test the others as I know they are 40-50 all the time if something breeds it may go higher.

The first packet was added on 16th of August. Last packet 30th of August. Each packet added 1 week apart and apparently it takes 3 weeks for a packet to become functional.


17/8/2014 - Nitrates 40-80 pack added for 24 hours no change expected
23/8/2014 - Nitrates 40-80 second packet added
30/8/2014 - Nitrates at 20-40 3rd packet added. At this point weekly water changes were started to reduce.
06/9/2014 - Nitrates 10-20
12/09/2014 - Nitrates 10-20
20/09/2014 - Nitrates 5-10 yellow!
28/09/2014 - Nitrates 10-20
2/10/2014 -- Nitrates 5-10
12/10/2014 - Nitrate 20
15/10/2014 - Nitrates 10-20
22/10/2014 - Nitrates 5-10
2/11/2014 - Nitrates - 10-20
12/1/2014 - Nitrates at 5-10

This was using an API liquid test kit so is margin for error on my part. The control they used stuck at 20 but I do have some plants so its possible they are helping out more noticeably than before as lower levels. No fish have broken out in anything or lost colouring. The strange behaviour by 1 catfish was eventually worked out to be unhappy at hiding places on offer. Increased them and it stopped. First thought was O2 but started again after a few days so anyone who has read that thread as well now knows the answer.

For larger tanks this is not really a cost effective option but I did note from the sachem link that their media was supposed to work as both at about 50L per hour flow through which is interesting. The bags my media is in greatly reduce the flow through so have to be broken up around the filter or reduce throughput.

The test kit is still capable of going red so is not just defective.

As for Risk of the pump becoming the single of failure yes it is. I recently read a thread on another forum encouraging people to switch back to under gravels. The reasoning behind it was solid enough. 2 power heads on under gravel plates your redundancy in event one dies the other carries on.

All filter systems and methods will have plus and minus points.

[TwoTankAmin]

darrel- your point about single point failure is interesting but when we apply it to your tanks, it has not been avoided. Your single point are your plants as they are your primary biofilter, your filter itself is doing minimal nitrification. If your plants have issues or many died because you were unable to continue their upkeep for a couple of weeks, they would fail.

Most plants will readily use ammonium (NH4) vs the bacteria which use NH3. Because most ammonia in water is normally in the form of NH4 and because plants can use this faster than bacteria will use NH3, the more plants in a tank, the less nitrifying bacteria there will be. The reason is simple, there is minimal NH3 left for them to process so fewer of them will be in the tank. It is simple to understand this by considering the "silent cycle" planted enthusiasts favor. But this really is a misnomer because one is doing almost no cycling in heavily planted tanks, especially the higher the light levels involved are (and of course all that goes with them).

So here is an experiment we could try (not really but its a good example). Pick one of your heavily planted tanks and I will pick one of mine with no plants and no substrate. The one condition is that both these tanks are established and hold full fish loads matched to the tank size. Then you will remove 50% of your plants and I will remove 50% of my bio-media. Neither of us will take any remedial actions except for our normal water changes and you will continue to add any fertilizers or co2 for your plants you like. Which tank will recover to showing no ammonia or nitrite first? My bacteria can double in 24 hours or so and it should not take more than a day or two for my tank to be close to normal. How long will it take for your plants to recover and for your tank to return to normal?

[dw1305]

Hi all,
This really is the last post from me, but

darrel- your point about single point failure is interesting but when we apply it to your tanks, it has not been avoided. Your single point are your plants as they are your primary biofilter, your filter itself is doing minimal nitrification. If your plants have issues or many died because you were unable to continue their upkeep for a couple of weeks, they would fail.

This isn't right on a couple of levels, the first is the plants, they are a component of the filter system, not all of it.

I don't feed, or maintain them on a regular basis, they are self sustaining.

The only likelihood that they would stop growing is if I had a failure of the lighting, and I think I would notice.

Because most ammonia in water is normally in the form of NH4 and because plants can use this faster than bacteria will use NH3, the more plants in a tank, the less nitrifying bacteria there will be. The reason is simple, there is minimal NH3 left for them to process so fewer of them will be in the tank.... But this really is a misnomer because one is doing almost no cycling in heavily planted tanks.

This really isn't true, any established planted tank (with a substrate) will support a huge and diverse range of micro-organisms in a complex ecosystem. All of ecology is a "shades of grey" world. If any-one wants a more complete discussion of this I'd recommend Diana Walstad's "Ecology of the Planted Aquarium".

Because of my work commitments the tanks in the lab. are often left for 2 - 3 weeks with no maintenance (including feeding the fish, water changes etc.), and I've never had any problems with this.

The second is that plants are a component of the filtration, not all of it, even if we accept the premise that the plants stop growing and the keeper doesn't notice, they would still be providing surfaces for de-nitrification, along with the substrate and filter media, and there would be a gradual increase of bio-load, which would cover

Which tank will recover to showing no ammonia or nitrite first? My bacteria can double in 24 hours or so and it should not take more than a day or two for my tank to be close to normal.

As long as I maintain oxygenated biological filter material I have a stable and resilient system, even without the plants. It would be sub-optimal, but it would still be tenable.

cheers Darrel

[TwoTankAmin]

When a tank is heavily planted the plants are the primary system for dealing with ammonia. This becomes most clear when one reaches the stage of having to add fertilizers which contain nitrate to feed the plants. The reason is simple, there is a lack of nitrate because the ammonia is not being processed by bacteria but by plants. And when plants consume ammonia they do not create nitrite or nitrate in the water the way bacteria do. This is obvious in a "silent cycle".

There is not an unlimited amount of ammonia in a tank and the more of it that is used by plants, the less that is available for bacteria. And the limiting factor in bacterial nitrification is ammonia. It doesn't matter if you have plants in the substrate or not, ammonia is still the key determinant of how much nitrifying bacteria may be in a tank.

And I find if an odd argument that one can avoid plant failure because they attend the tank but this would not be applicable to one who has a bare bottom tank without plants. But to conclude this discussion in which neither darrel nor I is willing to concede the other's point of view, I will end with an anecdotal report.

My 75 gal zebra pleco f1 tank contains 19 adult zebras. I am working a dry season in this tank and in the past 6+ weeks I have changed a total of 30% of the water- 15% twice. At the end of 5 weeks (and only one 15% wc) I wanted to be sure the TDS were rising but not nitrate before I did that day's 15% change. So I tested for nitrate for the first time in I cannot remember how many years. After that one 15% water change over 5 weeks nitrates read somewhere between 0 and 5 ppm. The tank has no plants and no substrate, runs at close to 85F now on its way to 90- exactly where did the nitrate go? My answer is that I have denitrifying bacteria in the Eheim canister on the tank. This filter first ran for over a decade on my 50 gal. high light, co2 added planted tank until I sold the co2 system 2 years ago. The filter was moved to the 75 gal. This filter gets cleaned twice a year and has since day one. I have not lost a fish in this zebra tank to date. So clearly there are also no issues with oxygen levels since these fish need high oxygen levels.

I would also like to state I do not disagree with darrel about the potential benefits of plants in tanks where they are appropriate nor the benefits a planted substrate provides. Where we disagree is where denitrification can be happening and where or where not this might represent a problem.

So let us just leave things on this subject by saying that we agree to disagree.

[dw1305]

Hi all,
This really is the last one from me.

I have had using the JBL BioNitratex media. Its practical for me due to low water volume. At £20 a box for 4 packets.........Huge water changes early on as I was close or above the 50ppm that is the max level the packets tolerated. Than as the last packet was added slowly reduced each week to not shock the fish.......Overall result on basic test kits are lower TDS by about 100. PH down 0.8 from 8 to 7.2 . Nothing to drastic do wonder what the solids are that have disappeared? - Nitrates however have dropped to the lowest in all setups. I rarely test the others as I know they are 40-50 all the time if something breeds it may go higher.

17/8/2014 - Nitrates 40-80 pack added for 24 hours no change expected
.........
2/11/2014 - Nitrates - 10-20
12/1/2014 - Nitrates at 5-10

This was using an API liquid test kit so is margin for error on my part.

This isn't a product I've used, or route I would contemplate going down, but apparently it is a biological filter material where the nutrient it contains feed the denitrifying bacteria within the resin bead media, once their number have built up.

If you work from the assumption that it is is removing NO3- ions, the TDS would fall, because we have reduced the number of ions in solution (and TDS meters measure conductivity). There would look to be a reduction in nitrate levels, but unfortunately test kits for NO3 aren't particularly reliable, mainly due to interference from other anions, so the actual figures recorded would need to be regarded as "ball-park" at best.

There is not an unlimited amount of ammonia in a tank and the more of it that is used by plants, the less that is available for bacteria. And the limiting factor in bacterial nitrification is ammonia. It doesn't matter if you have plants in the substrate or not, ammonia is still the key determinant of how much nitrifying bacteria may be in a tank.......

This is back to "shades of grey" argument, I think the situation is much more fluid than this suggests. There is a review paper here: Geets et al. (2006) "Strategies of aerobic ammonia-oxidizing bacteria for coping with nutrient and oxygen fluctuations"<http://onlinelibrary.wiley.com/doi/10.1 ... 0170.x/pdf>

Planted systems are really plant & microbe systems, and it is difficult to compartmentalise their individual contribution. In terms of their abilities to improve water quality, we are looking at "plant/microbe" systems having about an order of magnitude more potential than "microbe only" systems. (If any-one wants an overview of this I'd recommend Stottmeister et al. (2003) "Effects of plants and microorganisms in constructed wetlands for wastewater treatment "<http://www.jlakes.org/web/Effects-micro ... BA2003.pdf>).

My 75 gal zebra pleco f1 tank contains 19 adult zebras. I am working a dry season in this tank and in the past 6+ weeks I have changed a total of 30% of the water- 15% twice. At the end of 5 weeks (and only one 15% wc) ....... After that one 15% water change over 5 weeks nitrates read somewhere between 0 and 5 ppm. The tank has no plants and no substrate, runs at close to 85F now on its way to 90- exactly where did the nitrate go? My answer is that I have denitrifying bacteria in the Eheim canister on the tank. This filter first ran for over a decade on my 50 gal. high light, co2 added planted tank until I sold the co2 system 2 years ago. The filter was moved to the 75 gal. This filter gets cleaned twice a year and has since day one. I have not lost a fish in this zebra tank to date. So clearly there are also no issues with oxygen levels since these fish need high oxygen levels.

I'm sure you are right, and that it is the denitrifying bacteria in filter that are reducing NO3 levels (again with the disclaimer that NO3 tests aren't particularly effective). I'm not saying that it can't be done, you are a successful fish keeper and breeder which proves that it can.

You don't need advice, because you know what you are doing, and why you are doing it. For me things are a bit different, I'm not claiming to be an expert fish keeper, in fact quite the opposite I'm admitting to being a fairly shoddy one.

The fish I keep survive because I've provided a stable, resilient environment for them, using simple techniques that don't require test kits, and/or filter supplements or special filter media etc.

The real point is that any-one can use the "BOD concept" <http://www.planetcatfish.com/forum/view ... =4&t=35930> or the "Duckweed Index" <http://www.planetcatfish.com/forum/view ... 1&start=20> etc. you don't need to be an expert.

cheers Darrel

[bekateen]

Hi All,

Here's an update on my experimental tank:

Originally, I set up the tank on October 5th, a standard 15 gallon tank (24"x13"x13"), with 4" of small-grain gravel and lots of plants (2-3 each of frogbit, Anubias, Crypts, swords, banana plants, Java ferns, and some loose Java moss), plus some driftwood. The tank has 6 large Corys, each 3" long (TL) - not a particularly heavy bioload, but keep in mind that (1) the tank is filled with 4" of gravel, so there's nowhere close to 15 gallons of water in this tank, and (2) the gravel is sewn with lots of live Tubifex worms for the fish to graze on for food, and I know the worms contribute to the bioload. The tank has fluorescent lighting on approximately 6 hours per day and the temperature is around 75F. I'm using an Aqueon QuietFlow 20 for filtration.

During the first two weeks of operation, the tank was "seeded" daily with the bacterial mix I mentioned earlier, a product called MicrobeLift PL. The pH is maintained at 6.8 using a 1:1 mix of Neutral Regulator and Discus Buffer. I don't have any water test kits for hardness, so I can't give you those numbers, but my local tapwater tends to be on the softer end of the scale.

Since this was an experimental tank, I wanted to know how high nitrogen levels would get if I didn't change the water for a while. Well, I haven't done any water changes since the tank was established approximately 50 days ago. Here are the results (based on the API water tests): Ammonia - 0, Nitrite - 0, Nitrate - between 80 and 160ppm. This is not what I would call a success. And on top of this, a few of the plants have died, which is not something I was expecting.

I suppose the only positives I can offer are (1) that the fish in the tank appear to be healthy and normally active even with the high nitrate levels, and (2) in spite of the high nitrate levels, algal growth is minimal (maybe this explains why some plants died too).

These numbers have been stable for several weeks, so perhaps this is a temporary, fragile equilibrium. But it is NOT the result I was hoping for since the LFS owner who gave me this advice was maintaining his nitrates at zero with infrequent water changes using a similar system (okay, you may be thinking, "Was he lying to me?" I suppose that's possible, but I think not - I trust this guy on other advice and it wouldn't make sense for him to deceive me on this). Alas, I live far enough away from the LFS where I was getting advice that I won't be able to get back soon to receive feedback from the LFS owner.

If you recall, the goal of the experiment was not to "never have to do water changes," but (A) to create a tank where I don't have to worry about water quality spikes like I've experienced before, and (B) to get a tank that needs fewer water changes so as to minimize the impact of the occasional water quality changes seen in my municipal water, with the added goal of suppressing algal growth.

I suppose if you're keeping fish that don't mind nitrates, then this would be fine. But if this is as good as it gets, I'm not going to make a habit of keeping tanks like this.

I'm not done with the experiment yet. I'll keep the tank running a while longer and try to get back to the LFS in December and get feedback from the owner, then see how my technique meshes with his.

Cheers,
Eric

[TwoTankAmin]

Part of the problem you are seeing is that the bacteria you are wanting to have colonize in order to perform denitrification are some of the last ones to establish in tanks. Since you are aiming for your substrate to hold a lot of the bacteria you are looking to establish, it requires establishing the plant root systems. The normal route for this is to begin by planting the tank and then giving it a number of weeks for the plants to settle in. This involves root systems growing into place. Moreover, many aquarium plants are grown emersed and when we plant them those leaves tend to died off an submersed leave grow to replace them. In addition, new plants ususally come from nursuries or established tanks. They come chocked full or nutrients and many need no fertilizing for a while until they do root. In fact one can risk burning tender new root growth adding fertilizer too soon in some cases.

There are other reasons for allowing plants to establish in a tank before doing any cycling that might be needed and then stocking it. However, in densely planted tanks, cycling is not normally needed. Let me borrow a quote from Swiss Tropicals re matten filters which are intended to work the way nature does in substrate:

The term filter for a Mattenfilter is actually misleading. The purpose of the foam is not to filter the water as is often assumed. The foam serves as the habitat for a vast array of microorganisms that include bacteria, archaea, worms, ciliates, flagellates, and many others. These microorganisms live in a community that is based on biofilms. The biofilms are created by bacteria that secret extracellular polymeric substance (EPS), which is often called “slime”. The community forms a bioreactor that processes the waste and turns it into food and energy for its members, and ultimately into organic or inorganic products that are then used by plants, evaporate, or removed by water changes. It takes a considerable amount of time to establish this “filter community”; consequently, it is very important not to disturb it unless absolutely necessary.

(Blue is mine) From http://www.swisstropicals.com/library/mattenfilter/

The process works pretty much the same in one's planted substrate. It all takes time and the more one does to disturb the substrate, the longer the process will take. I think the gent who is advising you may have neglected to mention how long it took for his tank to settle into the pattern he describes. When such a tank has been running for years it is easy to forget what it took to get it to that stage initially. Bear in mind that what makes all of this work is that there are the right types of microorganisms etc. established and then that the needed balance between them is also in a proper range.

As for nitrate levels, this is a hot topic. Firstly, as has been noted a few times in this thread, hobby nitrate kits are notoriously inaccurate, especially at 20ppm and under for the total ion based kits. Secondly,just as with ammonia or nitrite, different fish are differently able to cope with different levels of nitrate.

All of this argues for a slower approach here in order to achieve the desired results.

Finally. I looked at the link for the Mircobe-Lift and was bothered by what I read. It claims the bacteria works for either 11 months or 22 months based on bottle size purchased. But a bacterial community should be self sustaining in a tank as long as it isn't grossly neglected. Consider the nitrifiers, once you have cycled a tank, how much nitrifying bacteria have you ever added to keep the tank cycled? And lets remember a biofilm is filled with a diverse variety of bacteria, even when we take no special actions that biofilm will naturally contain some number of denitrifiers which will establish over time.

[bekateen]

Part of the problem you are seeing is that the bacteria you are wanting to have colonize in order to perform denitrification are some of the last ones to establish in tanks.

Yes, I was aware of this. The LFS owner's advice I'm following dictates a daily application of the MicrobeLift PL for two weeks to help accelerate this process, but I think even that is insufficient. I was hoping that the 50 days which have passed since I started would be enough, but apparently not. Also, since some of the plants have died, obviously this reflects a delay in the root system establishment within the tank as a whole.

Moreover, many aquarium plants are grown emersed and when we plant them those leaves tend to died off.

I'm unfamiliar with the cultivation techniques for aquarium plants, so I'm not sure what you mean by this but I'd like to know more if you don't mind elaborating. However, I would have expected some leaf loss if for no other reason the stress of transplantation from one tank (the store) to another (my tank). In my case, some of the plants just plain died - obviously no leaf regrowth is going to occur there.

I think the gent who is advising you may have neglected to mention how long it took for his tank to settle into the pattern he describes. When such a tank has been running for years it is easy to forget what it took to get it to that stage initially.

I think you are right on with this too. So far, I haven't mentioned the LFS by name, mainly because the owner's technique is not mainstream among serious aquarists (just look at some of the responses in this thread), but also because if you don't live in or near the San Francisco, California area, then the store's name is of no significance or consequence. That's fine, because we all have our own way of doing things, and what works for one person, or with one fish sp., may not work for/with another. But if you have ever been to the fish stores in San Francisco, you've probably visited this store. It's what I'd call an "old school" style of fish store - a small building crowded with lots of small tanks, stacked floor-to-ceiling, almost every tank with its own independent filter system, lighting, and heating; IMHO, the tanks are amazing, although not necessarily well decorated for display; the fish are pretty healthy as LFS fish go (not like many large chain stores, where so many fish have clamped fins, ich, etc.).

My point is that you're right: many of these tanks have obviously been running for years, and I think that this guy's success is in large part tied to the vitality of those plants. And that's why I want to get back to his store, to ask the owner more about the plants, especially the mosses and other plants that have taken over many of his tanks (my plants just aren't growing that fast in my tank conditions, and I'm not interested in a carbon dioxide supplemented hyper-growth aquarium - that's not what I'm trying to achieve). Like you said, "All of this argues for a slower approach here in order to achieve the desired results." And as I stated in my previous post, I'm going to let the tank continue for at least a month more to see if the bacterial balance improves and the nitrate levels come down. Even the LFS owner told me that the values would rise initially, but he said that after a while (and I thought he meant a month or two, but obviously not), the values would gradually drop to nothing. Only time will tell.

...just as with ammonia or nitrite, different fish are differently able to cope with different levels of nitrate.

Exactly. I think my adult Corys (aeneus, trilineatus, and agassizii) and my adult banjos don't mind so much. But my juveniles wouldn't like it. Also, although I haven't risked it, I suspect my Scleromystax wouldn't like it either, if I let their tank get that bad (but they are too valuable and difficult to replace, so I keep their water really clean).

I... was bothered by what I read. It claims the bacteria works for either 11 months or 22 months based on bottle size purchased. But a bacterial community should be self sustaining in a tank as long as it isn't grossly neglected.

I wonder about this too. How I've interpreted this is as follows: (1) Of course the manufacturer wants to sell more of the product, so they instruct us to use it regularly, thus using it up and needing to buy more (by the way, the LFS owner has not so far advocated chronic reapplication of the product. His instructions were only to reapply a maintenance dose if any serious water changes are performed or if there is a problem with the tank); (2) I think it's human nature to believe that for things to happen, we have to intervene. And this week-by-week or month-by-month intervention gives us the "feeling" that we are actually doing something, so things should stay healthy. It ignores the fact that the bacterial colony should be self-sustaining as you point out, barring any sudden water chemistry shifts or changes to the tank (e.g., accidentally overfeeding, or a fish dying, or simply adding more fish to an already loaded tank); and finally (3) remember that this product is primarily an outdoor pond product. I suspect that the manufacturer is anticipating pond owners who do things like chronically overfeed the fish, and also natural environmental changes like seasonal temperature fluctuations, warm weather algal blooms, etc., that might disrupt the natural bacterial population; it's not that the bacteria will die in 11 months, but if you use their product on a monthly basis like they prescribe, you will run out of the product in 11 months and will need to buy more. Otherwise, it's hard to imagine that they are suggesting that our bacteria are going to die every 11 months.

Frankly, I'm enjoying this experiment, even though it's not "working" fully yet and it's not over. And ultimately, I would like to achieve plants that are as lush and green as the LFS owner's tanks. Only time will tell. Also, as this thread continues, I am learning a lot more about nitrogen dynamics in fish tanks, and for that I thank you all.

Cheers,
Eric

[bekateen]

Just a quick note. Water hyacinth are considered invasive, and illegal to sell, purchase, or transport in California... Larry

Hi Larry and all,
I think you folks will appreciate just how serious the water hyacinth problem is in my area of California. Stockton is the largest inland deep water channel and port in the state of California, and the second busiest port on the west coast of the United States. But our delta is so choked with water hyacinth that our mayor has proposed importing manatees (yes, manatees) to eat the aquatic weed - like a landowner renting goats to clear grass. The idea would never work for so many reasons, and fortunately it won't be pursued further. But I find it interesting because it reflects the desperation of our state and local officials as they try to control this plant pest.

Cheers,
Eric

[pleco_breeder]

I don't want to get too far away from this topic because I'm enjoying reading through the references which have been posted here. However, you should know that getting manatees for that purpose isn't as far-fetched as you would think. In the earlier part of the 20th century, there was legislation presented to congress (and it almost made it through) to import HIPPOS to the southeastern US to control the same weed. It was even being proposed as a cheap source of meat which could be harvested to curb the effects of the economic depression of the time.

Larry