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Hello everyone,

does anyone have some experience with Corydoras and UVC filtration?
Are there any benefits for the fish that can't be acquired with frequent water changes?
Here is what my thoughts were so far:
To me the concept of UVC filtration sounds very tempting on first thought, especially as a means of keeping down the number of bacteria in my tanks. Thats why I'm interested in some first hand information or some educated guesses from you guys.
On second thought: I assume that its the bacteria on the substrate, not in the water that pose the main threat to Corydoras. So what good is a device that is only able to kill bacteria in the water?

Cheers,
Lisa

I have two tanks - a big goldfish tank and a Cory tank with 10 Cory's.

I DO NOT have UVC on the CORY tank ... but I do have it on the Goldfish tank.

I don't think I have a problem with parasites in the cory tank - but the goldfish tank is another story. MULTIPLE hassles with parasites in that tank.

This is what I can tell you from my experience about UVC. I will never be without one for the goldfish tank, it has HELPED cure me of a lot of parasite problems.

It's expensive and if you do it ... you get what you pay for. I think you need at least a 25 watt UVC. Mine cost almost $300. DIY - you COULD make one I suspect for a lot less.

You need SLOW FLOW through it to kill parasites. So if you only have one filter that does all your mechanical / chemical / biological filtration, you're probably not gonna want to slow that one down enough to make a UVC effective. You will either have to get another canister filter or a pump that you can slow down to run the UVC. I have an Eheim 2215 filled with POND MATRIX that discharges through my UVC and the canister runs WAY SLOW - I have a flow indicator on the output that "spins" and restrict the discharge down enough to where it only spins about twice a second.

UVC is something else you will have to clean. The same stuff that builds up on the inside of your filter tubing builds up in a UVC. It will build up on the inside surfaces but the main problem is the UVC bulb buildup - that will restrict it's effectiveness. I recommend a UVC with a "wiper" so you can periodically pull the "wiper" and clean the bulb without having to disassemble the whole unit.

BUT ... you will also have to disassemble the unit from time to time to clean out the inside surfaces. So you need a UVC that is easy to take apart and put back together again without leaks.

You can buy a cheap UVC - I did ... didn't work till I went to a 25 watt unit and it cost me $300.

But I haven't had any more problems with parasites ... but I also regularly use PRAZI.

Crystal clear water - I thought it was crystal clear before but now ... whoa.

I don't plan on getting one for the cory's though - they just don't seem to have issues with parasites like the goldfish do.

Hope this helps some.

Hi all,

corymaniac wrote: ↑30 Sep 2017, 19:42 does anyone have some experience with Corydoras and UVC filtration?
Are there any benefits for the fish that can't be acquired with frequent water changes?
Here is what my thoughts were so far:
To me the concept of UVC filtration sounds very tempting on first thought, especially as a means of keeping down the number of bacteria in my tanks. Thats why I'm interested in some first hand information or some educated guesses from you guys.
On second thought: I assume that its the bacteria on the substrate, not in the water that pose the main threat to Corydoras. So what good is a device that is only able to kill bacteria in the water?

I've never used a UV steriliser, but I can answer some of the bacterial questions.

The amount of microbial activity in the aquarium will depend upon the nutrient supply (mainly the easily oxidisable compounds and dissolved oxygen).

The addition of any form of biocide (like UV) will change the composition of the microbial assemblage, but it only has a minor effect on their number, this is because you haven't changed nutrient supply etc, and even if you kill 99.9% of the bacteria the remaining 0.1% will quickly fill the available niche.

The same applies, but to a lesser extent, to unicellular algae and zoo-plankton in the water column. If the passage of water through the UV filter is slow enough, any cells (phyto or zoo-plankton) passing through the filter will be ruptured.

You can use UV as a "sticking plaster", but it doesn't address any of the more fundamental problems of tank health.

Personally I'm pretty convinced that an established tank with plants, a substrate, water changes and high levels of dissolved oxygen is the way forward, and that good things come to those who wait.

Have a look at Stephan Tanner's article on Aquarium Biofiltration (<http://www.swisstropicals.com/library/a ... iltration/>), it covers this whole area in more detail.

cheers Darrel

Hello everyone,

Thanks for the comments!

So if you only have one filter that does all your mechanical / chemical / biological filtration, you're probably not gonna want to slow that one down enough to make a UVC effective. You will either have to get another canister filter or a pump that you can slow down to run the UVC. I have an Eheim 2215 filled with POND MATRIX that discharges through my UVC and the canister runs WAY SLOW - I have a flow indicator on the output that "spins" and restrict the discharge down enough to where it only spins about twice a second.

I must admit that I find it hard to find information on the requested flow rate, number of Watt per L tank volume etc. Can you recomment any source of information?

Darrel, I have a few questions that were raised by your post.

The amount of microbial activity in the aquarium will depend upon the nutrient supply (mainly the easily oxidisable compounds and dissolved oxygen).

What effect does dissolved oxygen have on microbal activity, does it serve as a "nutrient", thus increasing their number?

The addition of any form of biocide (like UV) will change the composition of the microbial assemblage, but it only has a minor effect on their number, this is because you haven't changed nutrient supply etc, and even if you kill 99.9% of the bacteria the remaining 0.1% will quickly fill the available niche.

So the niche would be for microbes that live substrate bound? That of course would not be desirable.

Cheers,
Lisa

Hi all,

corymaniac wrote: ↑01 Oct 2017, 16:33 Darrel, I have a few questions that were raised by your post.

The amount of microbial activity in the aquarium will depend upon the nutrient supply (mainly the easily oxidisable compounds and dissolved oxygen).

What effect does dissolved oxygen have on microbal activity, does it serve as a "nutrient", thus increasing their number?

Yes, aerobic microbial activity is dependent upon the amount of oxygen. If you want a simple example when you have bio-nitrification you've gone from NH3 to NO3, so you've used three oxygen atoms and you've added three hydrogen ions (H+, a proton) to the water. (An acid is a "proton donor", so unless you have an alkali (a base) present (bases are "proton acceptors") pH will fall).

This is why scientists use Biochemical Oxygen Demand (BOD) as a measure of how polluted water is.

BOD values are in mg O2 per litre of "water". As an example raw sewage would be in the range 300 - 600 mgL-1 O2, treated sewage 20 - 60 mgL-1, a polluted stream (which supports some fish and invertebrates), ~10 mgL-1 and a clean water source less than 5 mgL-1.

Pure H2O can only hold about 15 mgL-1 of O2 (it depends upon temperature and atmospheric pressure), which means that a large amount of organic waste will strip the water of oxygen pretty quickly, unless you can continually replenish it at a faster rate than it is consumed.

corymaniac wrote: ↑01 Oct 2017, 16:33

The addition of any form of biocide (like UV) will change the composition of the microbial assemblage, but it only has a minor effect on their number, this is because you haven't changed nutrient supply etc, and even if you kill 99.9% of the bacteria the remaining 0.1% will quickly fill the available niche.

So the niche would be for microbes that live substrate bound? That of course would not be desirable.

There aren't really many free living bacteria in the water, they are bound to solid surfaces as biofilms.

cheers Darrel

Good evening,

There aren't really many free living bacteria in the water, they are bound to solid surfaces as biofilms.

Ok, I was vaguely aware of that, but I assumed the effect of UVC-filtration as a biocide can only effect bacteria (/Protozoa/algae) in the water. If numbers of bacteria in the water are negligible, UVC filtration shouldn't have any effect whatsoever?

Cheers, Lisa

Do you believe that you have bad bacteria in your tank? I ask because lots of laypeople seem to assume that bacteria = bad, but in a fish tank bacteria also perform all sorts of very, very important biological services, including breaking down ammonia. In marine tanks people use "live rock" which is literally just rocks coated in bacteria to assist in reducing ammonia levels.

For parasites, which disperse through the water in many cases, I can see how a UVC system would disrupt their lifecycle. Maybe it could do the same for certain sorts of algae that have a lifecycle that includes a motile, drifting phase, but I really just don't see a lot of good for it.

I'm with dw1305 that it's better to create a small, functioning ecosystem in the tank (good bacteria, plants, and obviously fish) than try to keep the tank "clean". I have a few research tanks that HAVE to be bare-bottom with nothing but fish, and they're a pain to keep good water quality in and I have far more issues with the fish in them. I also have a tank that began as a self-contained ecosystem, full of pond water from a dozen ponds, lots of plants, and plenty of added small organisms that we were finished with in General Zoology. That tank eventually became a guppy breeding tank without me doing anything but adding filtration (there wasn't any originally) since I was going to be adding food now. It's the easiest tank to care for. It's been running for months without a water change and the water quality measures keep coming back fine. The fry survival is also really high, I suspect in part because there are lots of little organisms for the fry to eat, supplementing their diet.

Hi all,

Lycosid wrote: ↑01 Oct 2017, 22:53 ........I'm with dw1305 that it's better to create a small, functioning ecosystem in the tank (good bacteria, plants, and obviously fish) than try to keep the tank "clean". I have a few research tanks that HAVE to be bare-bottom with nothing but fish, and they're a pain to keep good water quality in and I have far more issues with the fish in them. I also have a tank that began as a self-contained ecosystem, full of pond water from a dozen ponds, lots of plants, and plenty of added small organisms that we were finished with in General Zoology. That tank eventually became a guppy breeding tank without me doing anything but adding filtration (there wasn't any originally) since I was going to be adding food now. It's the easiest tank to care for. It's been running for months without a water change and the water quality measures keep coming back fine. The fry survival is also really high, I suspect in part because there are lots of little organisms for the fry to eat, supplementing their diet.

That is it.

My view is that diversity builds stability. If you can build in negative feedback loops, and avoid single points of failure, your long term chances of success are increased.

For the OP there is some more discussion of this in "Using deep gravel..." (http://www.planetcatfish.com/forum/view ... 21#p306921).

cheers Darrel

Hello everyone,

If you can build in negative feedback loops, and avoid single points of failure

Could you elaborate on this a bit please?

ok, first of all: I really appreciate all the information and opinions you people are giving me! Especially Darrel's explanation about microorganisms and oxygen. I had to take courses on chemistry, biochemistry and microbiology for 2 years back in University but never made that connection. Man, that was a lightbulb!

I read between the lines that you guys might be a bit worried about me attempting to run any kind of "sterile" aquarium if that would be possible. So maybe I should explain a bit about why I'm interested in UVC filtration. I didn't do this in the initial post because I assumed nobody would be interested in reading pages after pages about how I do stuff etc.

First of all, all my tanks (6 at the moment) are planted and have either gravel or sand as a bottom substrate.
I do not suspect any "bad" bacteria in my tanks, but I assume that some of them have exessively high numbers of bacteria, especially the fry tanks where I have to feed several times a day.
To give an example, I have a 60 L Tank, 4-5 cm high Sand on the bottom, a few plants, air driven sponge filter, has beens running for around 12-15 months.
At first I had 4 or 5 Endler Guppies in this tank that quickly became around 50 (I therefore moved them to a 150 L tank).
Then I used the tank to raise my Danio margaritatus fry. During 3 or 4 months I raised around 40 fry in there, being at the most 15-20 fry at once in the tank. When the fry become free swimming after they hatch, their mouths are too small for artemia naupli, so for around 1 week I feed them with sera micron, as soon as they can manage artemia naupli I change to a diet of around 80% artemia and 20% very fine flakes. Another thing abound D. margaritatus is that they don't eat off the ground which is why I have a few snails in their tank (trumpet snails and ramshorn snails).
About 8 weeks ago I began to encounter several problems indicating overfeeding in this tank: First I noticed that the snail population was exploding. A few weeks later the same happend to the algae and I had some cyano bacteria. Nitrates were between 10 and 15 (max 20), but I suspect excess amounts of phosphates which I cannot measure reliably. For the last 4 weeks or so I have been observing that the fry don't grow as fast as they used to and always look undernourished although they eat well.
Of course I increased water changes and reduced/optimized feeding etc. in this tank months ago, but the problem with the fry not growing/looking undernourished is still present.
I suspect excessive numbers of bacteria in this tank as the source of the problem and I think the only reason no fry has died is that they are not ground dwellers.
As soon as the fry are large enough to be moved (if that ever happens) I will empty and restart the tank . What bothers me is: what can I do if such a thing (basically me accidentally overfeeding) happens again, especially in a tank for ground dwelling fry like Corys?
Can UVC help to cushion my clumsiness? I do not want to risk any precious fry.

Cheers if you made it till the end of this post,
Lisa

Hi all,

corymaniac wrote: ↑02 Oct 2017, 15:06

If you can build in negative feedback loops, and avoid single points of failure

Could you elaborate on this a bit please?

If you have plants (and particularly ones with access to atmospheric oxygen) they will respond to increased levels of nitrogen (bioload) by putting on extra growth, which will deplete the extra nitrogen (it will be combined into the plant tissue). The plants will also produce more oxygen (via enhanced photosynthesis), which will allow for greater levels of microbial nitrification.

It is a negative feedback loop, higher levels of nitrogen lead to enhanced growth, which leads to greater uptake of nitrogen, which leads to more oxygen production and lower nitrogen levels.

Photosynthesis is the really important process in this, because of its oxygen production.

If you just have microbial nitrification, an increase in bioload leads to a depletion of oxygen, which leads to reduced nitrification which leads to a further depletion of dissolved oxygen and you can spiral into a positive feedback loop of increasing ammonia levels and decreasing oxygen levels.

If you don't have a substrate, or plants, and are reliant on microbial filtration in a single canister filter, you have a single point of failure (the filter). If you have more than one filter that reduces the risk, but you are still in danger from power cuts etc., if you have plants and a substrate you have added further sites for biological filtration and added resilience.

corymaniac wrote: ↑02 Oct 2017, 15:06I read between the lines that you guys might be a bit worried about me attempting to run any kind of "sterile" aquarium if that would be possible. So maybe I should explain a bit about why I'm interested in UVC filtration. I didn't do this in the initial post because I assumed nobody would be interested in reading pages after pages about how I do stuff etc.

First of all, all my tanks (6 at the moment) are planted and have either gravel or sand as a bottom substrate.
I do not suspect any "bad" bacteria in my tanks, but I assume that some of them have exessively high numbers of bacteria, especially the fry tanks where I have to feed several times a day.
To give an example, I have a 60 L Tank, 4-5 cm high Sand on the bottom, a few plants, air driven sponge filter, has beens running for around 12-15 months.
At first I had 4 or 5 Endler Guppies in this tank that quickly became around 50 (I therefore moved them to a 150 L tank).
Then I used the tank to raise my Danio margaritatus fry. During 3 or 4 months I raised around 40 fry in there, being at the most 15-20 fry at once in the tank. When the fry become free swimming after they hatch, their mouths are too small for artemia naupli, so for around 1 week I feed them with sera micron, as soon as they can manage artemia naupli I change to a diet of around 80% artemia and 20% very fine flakes. Another thing abound D. margaritatus is that they don't eat off the ground which is why I have a few snails in their tank (trumpet snails and ramshorn snails).
About 8 weeks ago I began to encounter several problems indicating overfeeding in this tank: First I noticed that the snail population was exploding. A few weeks later the same happend to the algae and I had some cyano bacteria. Nitrates were between 10 and 15 (max 20), but I suspect excess amounts of phosphates which I cannot measure reliably. For the last 4 weeks or so I have been observing that the fry don't grow as fast as they used to and always look undernourished although they eat well.
Of course I increased water changes and reduced/optimized feeding etc. in this tank months ago, but the problem with the fry not growing/looking undernourished is still present.
I suspect excessive numbers of bacteria in this tank as the source of the problem and I think the only reason no fry has died is that they are not ground dwellers.
As soon as the fry are large enough to be moved (if that ever happens) I will empty and restart the tank . What bothers me is: what can I do if such a thing (basically me accidentally overfeeding) happens again, especially in a tank for ground dwelling fry like Corys?
Can UVC help to cushion my clumsiness? I do not want to risk any precious fry. Cheers if you made it till the end of this post

I understand a bit more, I'd probably try to up the water change frequency and add some more plants (for the reasons above). A floater like Amazon Frogbit (Limnobium) and a sub-surface floater like Hornwort (Ceratophyllum) would be ideal, they are easy to harvest and will improve water quality.

cheers Darrel

I have a small UV unit I use in as needed situations. It was purchased to help "sterilize" a tank, to the extent possible, before the fish went in. The fish in question were newly imported wild Altum angels. There is an excellent explanation of UV use and how to calculate needed watts and optimal flow rates here http://www.americanaquariumproducts.com ... ation.html

I am not a fan of continuous use UV on a tank, however, there are specific applications for which it can be helpful.

Hello everyone,

I'd probably try to up the water change frequency and add some more plants

Thanks Darrel, got myself some Limnobium today. (I had to take out the Ceratophyllum though because it was covered with cyanobacteria.)

I have a small UV unit I use in as needed situations. It was purchased to help "sterilize" a tank, to the extent possible, before the fish went in. The fish in question were newly imported wild Altum angels. There is an excellent explanation of UV use and how to calculate needed watts and optimal flow rates here http://www.americanaquariumproducts.com ... ation.html

I am not a fan of continuous use UV on a tank, however, there are specific applications for which it can be helpful.

Thank you, that is valuable information.

Cheers,
Lisa