What’s caused the ammonia crisis that’s killing our catfish?
We have a 105l/23 gal tank which is running just great. We also have a small 28l/6 gal tank which is mainly for poorly fish, but recently our Bristlenose catfish bred so I moved 60 babies into it. The next day I found 10 dead and a further eight dead the day after that.
Our problem is ammonia – it was 6, but is now running at 3. We have put an Aqua-detox in the filter and I also put 20g of tonic salt in to see if that would help get rid of the ammonia.
All the other parameters are low, but they have been since the tank was set up around three months ago. How can I solve this problem? CHRIS KERRY, BY EMAIL
BOB says: It sounds as if your small tank is not ‘cycled’, the process whereby you allow the filter to become colonised with the vital beneficial bacteria which convert toxic ammonia produced by the fish to the relatively harmless nitrate. Keeping a small tank for emergencies in the manner you do is a good idea, but the filter will not be mature unless you regularly add small quantities of ammonia to the tank when it’s empty of fish to keep the bacteria fed. Suddenly adding a large population of fish means that the filter just can’t cope and the dangerously elevated ammonia levels and fish deaths you are experiencing are the inevitable result. Adding the Aqua-detox will help to remove some of the ammonia, but will not solve the problem of the immature filter. My advice would be to carry out immediate daily 50% water changes with dechlorinated water to keep on top of the ammonia problem, while the filter starts to catch up.
Bristlenose catfish need well aerated water with a current to thrive.