Backyard Aquaponics
A place to discuss aquaponics

Trying to figure out what killed of my Channel catfish. The fish were placed in three areas: 1) my aquaponics tank{100gallons}, 2) an small pond, and 3) in a pool that we raise water-lilies in. the catfish as they died off had their slime-coat turn white, their gills took on a slightly brownish color and they seemed to have difficulty breathing (they were gulping at the air). I know that the problem was not oxygen content because the pond and pool both have other fish in them that are still doing well( the pool even has a new batch of baby minnows swimming at the surface looking for food and goldfish that only pop-up to the surface for food). Any Ideas? First time trying aquaponics out and I'm going crazy trying to figure out what happened.

Hi Azucalos, sorry to hear about your fish.

It sounds like it could have been Nitrite poisoning also known as brown blood disease or Methemoglobinemia. Hemoglobin combines with nitrite to form methemoglobin (which is brown in color and causes the gills to turn brown. Methemoglobin either can't carry oxygen or doesn't do it well - I'm not sure about which ). The gist of this is that the fish can't get enough oxygen and wind up dying. Overfeeding can cause this or a buildup of organic matter of some kind that results in excess Nitrites.

Hope this helps

http://www.aces.edu/dept/fisheries/aqua ... nBlood.pdf

Plus one to nitrate toxicity. .. BUT

But I would suggest you post some readings to help identify the cause.. clearly it is upsetting and you wonder why some fish are affected and not others..
I have a system where KOI are thriving but other fish die in 4 days and there are NO bad readings..

I do wonder about the fact that it is three unconnected (assumed) systems and it has happened in parallel..
So that would make me wonder how long the cats were in there... and if there is another issue..

PS... especially suspicious about the water Lilly pond, where I would have thought NITRITES. And. The likes, would not be an issue but O2 sure could be an issue.. but. I don't think O2 deficienccy leaves the gills brown..

Warning.. I am far from an expert, and more a drip-under-pressure
..
.

Nitrite BuiDoi?

Thanks for the help. I got the fish on the fifteenth and noticed one dead after I got home with them. I placed the bag they were in in the aquaponics tank for about 18-min. I then removed the 30 catfish from the bag and placed them in the tank. I saw the water took on a brown tinge later in the aquaponics tank and did a water change because of it. {most likely excess food that I started them on the next morning} I transferred a few to the other areas when I started to see a die-off not thinking about it.(panic attack- all run no think). from what you guys said most likely they were already at toxic levels and the deaths in the other areas were just the fish finally succumbing to the toxins. The tanks readings just before I dumped the water were unfortunately not taken, but the ph at the time of the die-off begining was 6.7-6.8 range. ( anger that i couldn't keep a fish that was supposed to be as sturdy as a rock alive) The amount of food that I had gave out was at best guess 1-2oz of pellets, or for a visual refrence about the amount that would fit in a cough-syrup cup in morning and at dusk. And if I remember correctly the water changed color about Saturday so I had had them for about 3-days at that point.

Tough to say for sure but I do think it was nitrites. Salting to 1ppt (1KG per 1000L or 1gm per L) with uniodized salt that has no added caking agents will help prevent nitrite toxicity and also help the fish with stress. Did you add any seaweed or iron supplements to the water? Sometimes doing that will turn the water brown.

You may have had another fish die without your knowing it so it may not have been the feed. The end result is the same. For what it's worth, it's good practice to remove any feed that is uneaten. In older system this can often be taken care of by the biofilter but with a relatively young system that may not be fully cycled

!!!!!! found a catfish in my mom's lily pool at the surface moving about! I couldn't tell if it was gaping for air or trying to eat a few baby minnows that were at the surface. so might not be all lost. After asking her about it she said she thinks she found three dead in the pool. I put 5-6 in there! I think leaving them in there is best i can do for them.

scotty435: I have had the system up and running since about the middle of May with 6 goldfish running it. After I got the catfish I transferred 5 to the pool and 1 to an aquarium on my desk were he seems to enjoy playing in the bubbles made by the airstone in it.

- glad you found some still living.

You probably were cycled but older system to me usually means 6 months to a year or longer. Cycling is done long before this but system stability gets better over time. When you get a big batch of fish and your system has only had a few, it takes awhile to get the bacterial numbers required to process all their waste. It's a good idea to start out slow on feeding to avoid overloading the filter, you might even want to hold off feeding for several days while the fish adjust. They'll still produce some waste during this time to help build your bacteria up.

Cheers

Indeed.. nitrite... almost a Freudian slip. But knowing Nitrite because of the reference.

I am ironically worried about NITRATES.. OR. Rather interested in them, having unwisely pressed ahead with my plant-less system.. and watched the "cycle" undulate and stabilise.. and now wonder just how I will react to ultimate NITRATES..

When I got my latest lot into my new system, I ensured there was SALT and the pH was as low as possible, and fed them near nothing.. it paid off.. but
There is that urge to feed.. they must need feed... poor little things..???

I have to say that in this case, I still can't see the link between the deaths, in three locations.. but understand that the initial damage done can take days to actiually kill the fish, and so i wonder if the damage was already done, and despite separation to three locations, the process had already commenced, and it simply became a case of which if any, might survive..

PS.. reading the thread again, I don't see any actual readings other than pH..
This would leave me thinking "..no test kit.."
So' you are flying in the dark to a large extent.. and thus it could be worth looking into a test kit, like the API one..
That will give you the unknowns ..
..
.

Absolutely true BuiDoi, just going by best guess, based mostly on the color of the lungs and the statement that there was plenty of aeration but the fish were gulping air at the surface. An API master test kit would be a good idea.



Fish don't need to maintain their body temperature like we do so they need less energy and can go for long periods without food.

Well, you could try to eliminate some of the waste in various ways before it can be processed into nitrates. You could collect and dump the solids in your compost bin and trap and denitrify the suspended solids using a slightly anoxic bio-filter. It might be a bit tricky but I think you could manage it.