Catfish "gasping" a lot for air. Normal? Because they stopped now.

[SuperNaeni]

Ok, this is probably the stupidest question of the day, but i am still pretty new in the aquarium world. I've got some rtcxtsn and a rtc and a tsn. They have all kind of gasped their entire 4-5 month life. They have constantly opened and closed their mouths in a rythmic fasion. And even though he's not a catfish, my oscar has as well. A couple of days ago, i put in an air pump and we now have a good stream of air bubbles into the tank. And today, all of a sudden, they have all stopped this rythmic "gasping". Now all of them have their mouths completely shut all the time and they seem much calmer.

My question is: did i torture them before with oxygen-low water? Or is it normal that they are sort of gasping all the time and something is wrong with them all now?

I had no experience with catfish before these, so i just thought it was normal that they were doing this gasping thing all the time. My two filter pumps were completely submerged, so no air bubbles has come from them before.

[Bas Pels]

Although I think torturing is quite a strong word, the water did obviously contain too little oxygen, and now it looks like the oxygen is sufficient.

[Viktor Jarikov]

No. Gasping is not normal. You must have not had adequate stirring / agitation.

A bubbler does not oxygenate water through the bubbles themselves to any significant extent but through bubble movement. What it does is it stirs water efficiently pushing down the most oxygen rich upper water layer and pulling up the least oxygen rich bottom layer. One does not need bubbles per se to accomplish this. Properly sized and used, and aimed power head as well as the filter output can accomplish the same.

The disturbing thing is that fish may still suffer from inadequate oxygen but not gasp. That's why it is always better to err on the safe side and provide ample, plenty stronger than "recommended" agitation... without overdoing it, e.g., blowing fish around a tank with a 1000x turnover.

[Bas Pels]

A bubbler does not oxygenate water through the bubbles themselves to any significant extent but through bubble movement. What it does is it stirs water efficiently pushing down the most oxygen rich upper water layer and pulling up the least oxygen rich bottom layer. One does not need bubbles per se to accomplish this. Properly sized and used, and aimed power head as well as the filter output can accomplish the same.

I once saw a calculation trying to proove this. It is written everywhere, but the attempt to proove it trned out to be a disproovement.

The bubbles live for a short while, but at every time there are a lot of them, therefore at any time there is oxygen going into the watrer at the bubble surface
The bubbles are small - but that just implies there is a lot of bubble surface.
contrarily to the surface of the tank - where the warer is relatively rich in oxygen, the water around the bubble is much less rich, as the bubble starts near the bottom

The calculation (which has gone from the internet, and I will not try to repeat it) results quite often in an extra gas exchange through the bubbles which is of the same size as the tank surface has.

From my personal experience, I can only admit that providing bubbles does add a lot of oxygen to the water - whether through water movement (direct help) or through surface movement (indirectly, asVictor put it).

The problem is, however, comparing water movement through a canister filter with bubbles, the bacteria in the canister will use oxygen, and therefore the water coming from the canister is poorer in oxygen than the water going into it. If one would use a spray-bar, that is, let the water flow along the surface, this is not a big problem. But in case one would put this stream lower, this can be a problem.

Therefore, it is hard to compare a canister filter with an air driven filter

[Viktor Jarikov]

Thanks, Bas. I forgot there is a difference of opinions on how much "direct" effect there is from bubbles. And the point on the position of the filter output is also important. If filtered water returns to the tank water well below the surface and does not agitate the surface much, it's asking for trouble with dissolved oxygen IMHO.

[dw1305]

Hi all,
There is quite a lot of work on the use of bubblers in the "waste water" industry (where you have "water" with a huge BOD). This is from Gresh, M. et al (2011) "Effects of aeration patterns on the flow field in wastewater aeration tanks" Water Research 45:2

Due to the high energy input of aeration, the spatial distribution of air diffusers largely determines the flow field in aeration tanks. This has consequences on the efficiency of the aeration system, the performance of the aeration tank and on tank operation and control. This paper deals with these effects applying both Computational Fluid Dynamics (CFD) enhanced with a biokinetic model and full scale validation using velocity and reactive tracer measurements with high temporal and spatial resolution. It is shown that small changes in the diffuser arrangement drastically change the overall flow field.....

Basically to get much oxygen dissolving from air (~21% O2) bubbles you have to have very small bubbles (oxygen isn't very soluble), and a very long "residence time" in the water column.

I wrote an article that attempts to quantify the processes that lead to oxygenation and de-oxygenation in the aquarium - "Aeration and dissolved oxygen.....", it has had a few homes but currently resides at <http://plecoplanet.com/?page_id=829>.

cheers Darrel

[bekateen]

So this raises some questions for me. I'm supposing that the diffusion constant for oxygen into water will be the same at the aquarium surface and at the bottom of the aquarium, from air bubbles. I'd also suppose that the summed surface area from water bubbles to surrounding water (when counting all the air bubbles underwater at the same instant) can be less or more than the surface area of many aquaria (depending on the type of bubbler used, air pressure through the bubbler, and the dimensions of the tank of course). And as someone else stated, I would expect that the oxygen concentration in water at the bottom of the aquarium is probably slightly if not significantly lower than the oxygen concentration in water at the aquarium surface, thus providing a stronger oxygen concentration gradient between the bubbles and the water than between the overlying air and the aquarium surface. Granted, the bubbles rise quickly, so no one bubble exists for very long. But if the bubbler is continuously producing bubbles, then I would imagine you can calculate what I'll call a "standing population" of bubbles that you would expect to exist at any one moment.

Accepting Darrel's comment (from his article) that smaller, finer bubbles are far more effective at aerating water than are larger bubbles, wouldn't we still expect even typical (not particularly tiny) bubbles with a high standing population (i.e., you're making a lot of bubbles) contribute significantly to water oxygenation, relative to that provided at the surface?

Cheers, Eric

[dw1305]

Hi all,
There definitely are ways of increasing the residence time of the bubbles in the water, but usually a quicker turn over of water, or a process that produces oxygen (usually photosynthesis) gives you more "bang for your buck". Plants are a win-win situation because they are simultaneously producing oxygen and stopping NH3/NH4+ entering nitrification.

If I was to keep fish with a high BOD I would have a planted "wet and dry" trickle filter. Any type of wet and dry trickle filtration has a huge gas exchange surface and because of this is an order of magnitude more efficient than other types of biological filtration. By adding plants, with access to atmospheric levels of dissolved gases, you've raised the bar again.

Biological filtration is really all about oxygen, which is why the metric for water pollution is Biochemical Oxygen Demand (BOD).

cheers Darrel

[Bas Pels]

But if the bubbler is continuously producing bubbles, then I would imagine you can calculate what I'll call a "standing population" of bubbles that you would expect to exist at any one moment.

Accepting Darrel's comment (from his article) that smaller, finer bubbles are far more effective at aerating water than are larger bubbles, wouldn't we still expect even typical (not particularly tiny) bubbles with a high standing population (i.e., you're making a lot of bubbles) contribute significantly to water oxygenation, relative to that provided at the surface?

Cheers, Eric

I think this is the key element: each bubble has a life of, say, 10 seconds, but on each and every moment a given tank can contain, say, 600 or more bubbles.

Obviously, having tinier bubbles does have - for a given amount of air - have a few advantages: Firsty, the total of all the bubbles will have a larger surface, but secondly tiny bubbles rise more slowly than big ones.

I can therefore imagine, it would be better to use a fine airstone than a course one - even though the fine one will have a much higher resistance.

Biological filtration is, indeed, all about airation. The water does contain X polution which demands Y oxygen. In a canister, the required oxygen can only be taken from the water, but in any open filter - whether a sump, a biological filter or an inner filter, the oxygen can be replenished, making these filters much more desirable.

In an dry/wet type of filter an exellent contact between air and water is provided, but at a cost: the water is falling down, and has, therefore, to be raised again.

Water is rather heavy, and now I'm wondering - will an airstone, which uses only a little energy, suffice to improuve the airation? It would be much less costly in terms of energy

[bekateen]

I think this is the key element: each bubble has a life of, say, 10 seconds, but on each and every moment a given tank can contain, say, 600 or more bubbles.

Obviously, having tinier bubbles does have - for a given amount of air - have a few advantages: Firsty, the total of all the bubbles will have a larger surface, but secondly tiny bubbles rise more slowly than big ones.

I can therefore imagine, it would be better to use a fine airstone than a course one - even though the fine one will have a much higher resistance.

Water is rather heavy, and now I'm wondering - will an airstone, which uses only a little energy, suffice to improuve the airation? It would be much less costly in terms of energy

I doubt it's economical monetarily, but one arrangement I use is an airstone positioned beneath a submerged power head (e.g., a Hydor Koralia Nano recirculating pump). The power head disrupts the bubbles, making them smaller, and shoots them horizontally into the aquarium along with the water current, increasing the "life span" of the individual bubbles before they finally rise to the surface (not to mention the obvious benefit of increased water circulation, which only helps aeration in this case anyway). My hope is that the combination of disrupted (smaller) air bubbles, mixed with a forced horizontal (and slightly downward, in my tank) water current provides a healthy level of oxygenation for the fish.

Of course the pump also adds heat to the tank, which can have a negative effect on oxygen solubility, but since the tank is already heated to a temperature greater than can be achieved solely using the pump, the net effects are that 1) the water temperature is no warmer than I desire (thus no additional loss of oxygen solubility) and 2) my aquarium heater doesn't run as long to heat the water.

Cheers, Eric

[Bas Pels]

Using a pump as heater is a very economical way to dissolve oxygen, in my eyes.

If one would use a standardheater, this would cost a certain amount of electricity, and therefore money. If this electricity would be spend on a bigger pump, this would increase water flow, but the pump would also produce heat. Some of the electricity would go into heating, the rest into flow. However, this flow will in the end, through friction, be turned into heat too.

Therefore, the flow is basically free.

Obviously, one would like to have a heater for certainty, but the free flow would help lots in getting oxygen nito the water.

But, tyhat is only my opinion

[dw1305]

Hi all,

In an dry/wet type of filter an excellent contact between air and water is provided, but at a cost: the water is falling down, and has, therefore, to be raised again. Will an airstone, which uses only a little energy, suffice to improve the airation? It would be much less costly in terms of energy

That is one reason why I used over-tank trickle filters, rather than a sump. You don't have to lift the water very far, and it returns to the tank under gravity. In small tanks you can use an air powered "DeBruyn" type filter, which was actually where I started. We needed a pump to deal with the "water" when we worked with "landfill leachate".

I think an air pump, via something like the "Swiss Tropical" <http://www.swisstropicals.com/?PlanetCatfish/> jet-lifter system, is probably the most economical way to provide aeration.

I doubt it's economical monetarily, but one arrangement I use is an airstone positioned beneath a submerged power head (e.g., a Hydor Koralia Nano recirculating pump). The power head disrupts the bubbles, making them smaller, and shoots them horizontally into the aquarium along with the water current, increasing the "life span" of

I do the same, I have a venturi (on a Maxi-jet power head) and this ensures that a lot of bubbles end up trapped under plant leaves, and on the pre-intake sponges of both power-head and external filter. You ideally want the air in side the filter, but this causes problems with air-locks etc unless it diffuses in.

Because I came back to fish-keeping via my work, it had never occurred to me that people would use their external filter as a syphon, and I just assumed that every-one would have a large coarse sponge as a pre-filter.

You want oxygen and ammonia in the filter, you don't want anything else. The more oxygen, and less ammonia, you have the better.

High levels of dissolved oxygen give you resilience, which means that if the bioload increases dramatically (undiscovered dead fish, or emergency chloramine dosing of the water supply) you don't get into a positive feed-back loop of oxygen depletion and fish death leading to further oxygen depletion and fish death etc.)

cheers Darrel

[Viktor Jarikov]

There definitely are ways of increasing the residence time of the bubbles in the water, but usually a quicker turn over of water, or a process that produces oxygen (usually photosynthesis) gives you more "bang for your buck". Plants are a win-win situation because they are simultaneously producing oxygen and stopping NH3/NH4+ entering nitrification.

Submerged plants consume a lot of oxygen at night, so you are probably talking of either 24/7 lighting or above-water plants, Darrel, aren't you?

If I was to keep fish with a high BOD I would have a planted "wet and dry" trickle filter. Any type of wet and dry trickle filtration has a huge gas exchange surface and because of this is an order of magnitude more efficient than other types of biological filtration. By adding plants, with access to atmospheric levels of dissolved gases, you've raised the bar again.

You've stated this many times and I've taken it to heart but how would one combine a need to turn over 15,000 GPH with a trickle filter in a DIY, cheap manner? I guess the question is whether trickle filters in hobbyist hands are confined to small tanks with small turnovers?

Biological filtration is really all about oxygen, which is why the metric for water pollution is Biochemical Oxygen Demand (BOD).

Thanks, Darrel. It's an eye opener and a real fish-life saver to remember this. We are so focused on ammonia and nitrite, biomedia type, amount, and surface area, turnover, etc. I wonder why the paramount importance of oxygen is so poorly conveyed (IMHO) in the vast majority of write-ups on biofiltration in our hobby. Perhaps, it's just me. The place and person I learned it from is here and you. Much obliged.

[Bas Pels]

Biological filtration is really all about oxygen, which is why the metric for water pollution is Biochemical Oxygen Demand (BOD).

Thanks, Darrel. It's an eye opener and a real fish-life saver to remember this. We are so focused on ammonia and nitrite, biomedia type, amount, and surface area, turnover, etc. I wonder why the paramount importance of oxygen is so poorly conveyed (IMHO) in the vast majority of write-ups on biofiltration in our hobby. Perhaps, it's just me. The place and person I learned it from is here and you. Much obliged.

Actually, This forum is the first one where I read about ammonia. I think there are a few differences between Europe and the USA where it comes to fish keeping.

Generally speaking, we keep the same fishes in lager tanks, with less water replacement.

The result is, a larger tank, which is kept for a while, will have all the bactgeria needed for turning over ammonia rapidly - so ammonia will not be that much of an issue.

Obviously, if one keeps large fish, such as tankbusting catfish, this might still be an issue

However, our water is - again, generally speaking - older and therefroe it will contain more organic material. That will result in a lower saturation in oxygen - and therefore less oxygen in the water. Therefore, we Europeans are more used to trying to approach a satruration of our water.

The above is a crude generalisation, most likely it will fit 50 % of the fish keepers. And to make matters worse, it is an impession I got through forums - I never went to the USA to verify my assumptions

[dw1305]

Hi all

Submerged plants consume a lot of oxygen at night, so you are probably talking of either 24/7 lighting or above-water plants, Darrel, aren't you?

Reversed lighting regimes or just emergent plants (with their roots in the water) use less dissolved oxygen, but aquatic plant respiration actually makes a fairly minor contribution to dissolved oxygen usage outside of the photo-period.

This is because a lot of the oxygen cellular respiration uses at night is all ready present in the plant tissues, following photosynthesis, and that the water will be fully oxygenated at the end of the photo-period. I think this one should be available <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659369/>.

Planted tanks will still have a positive oxygen balance (at night) long after a non-planted tank with a similar bioload, microbial filtration and water turn-over would be in oxygen deficit. I know this is true, but it is often really difficult to convince people.

If I was to keep fish with a high BOD I would have a planted "wet and dry" trickle filter.

You've stated this many times and I've taken it to heart but how would one combine a need to turn over 15,000 GPH with a trickle filter in a DIY, cheap manner? I guess the question is whether trickle filters in hobbyist hands are confined to small tanks with small turnovers?

You would think there must be large scale trickle filters you could construct, they are widely used in the waste water industry. <http://www.eoearth.org/view/article/171151/>
This sort of of high tech application, as well as, traditional clinker sewage beds, "vertical flow constructed wetlands" etc. I'll have a look through the literature for DIY waste water solutions in places without main-drainage etc. There must be something suitable.

Biological filtration is really all about oxygen, which is why the metric for water pollution is Biochemical Oxygen Demand (BOD).

Thanks, Darrel. It's an eye opener and a real fish-life saver to remember this. We are so focused on ammonia and nitrite, biomedia type, amount, and surface area, turnover, etc. I wonder why the paramount importance of oxygen is so poorly conveyed (IMHO) in the vast majority of write-ups on biofiltration in our hobby. Perhaps, it's just me.

No, I'm clueless as well. We've just got to keep on spreading the word.

cheers Darrel

[dw1305]

Hi all,

Actually, This forum is the first one where I read about ammonia. I think there are a few differences between Europe and the USA where it comes to fish keeping. Generally speaking, we keep the same fishes in lager tanks, with less water replacement........The result is, a larger tank, which is kept for a while, will have all the bacteria needed for turning over ammonia rapidly - so ammonia will not be that much of an issue.....However, our water is - again, generally speaking - older and therefore it will contain more organic material. That will result in a lower saturation in oxygen - and therefore less oxygen in the water. Therefore, we Europeans are more used to trying to approach a saturation of our water.

I know it is a generalization, but I think there is a certain amount of truth in these national stereotypes. I also think some of it probably relates to the types of filters that are popular. In the UK we don't tend to use Bio-wheels and HOBs that they use in the USA, which are filter types which tend to lead to fairly efficient microbial biological filtration, mainly because the water is oxygenated. I assume the situation is similar in Europe to the UK. Again we don't tend to use HMF very much in the UK (or USA), and again they are filter type that can produce stable conditions.

Again it is a gross generalization but I tend to look towards Europe for "best practice" in fish keeping. This may be bias from my "day job", where a lot of the high quality research also goes on in Europe. That isn't meant to denigrate the many fine fish keepers (or scientists) in the rest of the world, it is just an opinion.

cheers Darrel

[bekateen]

In the UK we don't tend to use Bio-wheels and HOBs that they use in the USA, which are filter types which tend to lead to fairly efficient microbial biological filtration, mainly because the water is oxygenated. I assume the situation is similar in Europe to the UK. Again we don't tend to use HMF very much in the UK (or USA), and again they are filter type that can produce stable conditions.

Again it is a gross generalization but I tend to look towards Europe for "best practice" in fish keeping. This may be bias from my "day job", where a lot of the high quality research also goes on in Europe.

Hi Darrel,
Please excuse my difficulty with understanding your point here. Personally, I've only used HOB filters, bio-wheels, UG filters, and traditional sponge filters with airlifts. They all work, to one degree or another, but if I could settle on a better arrangement I would. So from your comments, I'm trying to figure out what this European "best practice" looks like? What type of filter is it that you feel represents best practice? Is it a HMF?
Thanks, Eric
P.S., I suspect that there is no one-size-fits-all answer to my question. Also, no denegration taken.

[dw1305]

Hi all

Hi Darrel,
Please excuse my difficulty with understanding your point here. Personally, I've only used HOB filters, bio-wheels, UG filters, and traditional sponge filters with airlifts. They all work, to one degree or another, but if I could settle on a better arrangement I would. So from your comments, I'm trying to figure out what this European "best practice" looks like? What type of filter is it that you feel represents best practice? Is it a HMF?

Hi Eric,
Just for the moment I'll ignore chemical and mechanical filtration, and just look at biological filtration. I'm also going to ignore anaerobic denitrification of nitrate (NO3). If people are interested in why, or why not, it may be a good idea inside the filter, we have Eric's thread here: <http://www.planetcatfish.com/forum/view ... =4&t=41038>.

Microbial Biological Filtration
Media
In practical terms the porosity and volume of the filter media are relatively minor factors and in most situations there will be sufficient potential sites for microbial colonisation.

Dissolved Oxygen
In most cases the factor that limits biological filtration will be oxygen availability. When we look at a microbial filtration system, the key metric is the gas exchange surface area to water volume ratio. The higher this ratio is the more capacity the system has to deal with the bioload (BOD - Biochemical Oxygen Demand).

It is at the gas exchange surface that gases will diffuse in and out of the system, dependent upon the gas diffusion gradient between the atmosphere and water. In a system with a high bioload the water will rapidly become both oxygen depleted and CO2 rich, so we need a large surface area where diffusion can occur.

We can increase the effective surface area of the tank by turning over the water volume relatively rapidly, but there are limits to this.

If we design a filter system so that we have a thin film of water moving over a complex surface exposed to the atmosphere we can increase the gas exchange surface massively. You can think of it as analogous to gas exchange in our lungs, the lungs are a relatively small 3 dimensional organ, but if we flatten them out they will cover a tennis court.

Because of their design biowheels, HOBs and "wet and dry" trickle filters all have relatively large gas exchange surface to water volume ratios. The same applies, to a more limited degree, with an air powered sponge filter or UG filter plate.

The situation is slightly different with HMF's, and is more analogous to what happens in an established substrate. As the HMF filter sponge matures it will still have access to aerial gases at the top, but in the sponge itself you will have changing boundaries where aerobic nitrification and anaerobic denitrification are occurring. <http://poretfoam.com/hamburg-matten-filter.php> & <http://www.swisstropicals.com/filtratio ... lter-shop/>.

Canister filters
The media in canister filters doesn't have any access to atmospheric oxygen, therefore in a canister filter we need to ensure that the water flowing in is highly oxygenated, and the residence time inside the filter isn't so long that the water becomes de-oxygenated whilst in the canister.

Why planted "wet and dry" trickle filter work so well.
The other thing that you have to factor in is that aerobic microbial biofiltration is about an order of magnitude less efficient than combined microbial/plant systems. This is why the "gold standard" for biofiltration is a planted wet and dry trickle filter.

This combines:
A large gas exchange surface.
An undisturbed "substrate" where aerobic nitrification and anaerobic denitrification will occur.
Plants with access to atmospheric levels of oxygen and CO2.

cheers Darrel

[bekateen]

Hi Darrel,
Thanks for the thorough explanation, and thanks for referencing my old thread on denitrification. (BTW, I still want to know how the LFS owner manages to pull that off, but I live too far away to see him more often).

Thinking back to oxygenation and filtration habits (the point of this thread), and referencing the comments earlier about the habits of aquarists on different continents, this makes me realize that I've never been to a home where anyone uses a planted wet/dry trickle filter. I'm sure many Americans have them, but none of my friends, family, or acquaintances do. I'm guessing that the LFS owner I referenced uses a strategy like it, since many of his tanks have plants growing up out of the water.

Cheers, Eric

[Shane]

Just a couple of points.

U.S. and U.K. aquarists use different filtration systems not so much because of different "best practices" but because our aquariums are physically constructed differently. A typical UK tank can't accept a US style HOB because they have glass bracing all around the lip of the tank and sometimes even across the center of the tank. Most of my filters would not even fit on most of Jool's tanks.

Secondly, I see alot more internal or "closed" filtration systems in Europe where capturing heat all year round is more cost effective. External HOBs turn the filter body into a manifold helping the ambient temperature cool the tank.

For many US aquarists cooling their tanks six months a year is more cost effective than capturing additional heat for the 2-3 months a year we need it.

-Shane

[dw1305]

Hi all,

Secondly, I see alot more internal or "closed" filtration systems in Europe where capturing heat all year round is more cost effective. External HOBs turn the filter body into a manifold helping the ambient temperature cool the tank. For many US aquarists cooling their tanks six months a year is more cost effective than capturing additional heat for the 2-3 months a year we need it.

Very true, trickle filters etc are very efficient air conditioning units, and in between that and the constant "soothing" sound of falling water I rapidly went over to a canister filter at home.

cheers Darrel