Originally Posted by Jhilsdon
I was using cuprazin and it seems as he's had a bad reaction to it.
Just done water test and hear are the readings
Just mixing up 40 litres of water for a water change to night any more I could do?
Well, with ammonia levels present, that is what is causing the labored breathing and lethargy. Your fish is suffering from ammonia poisoning, you need to do water changes until it reaches 0 and keep it at 0 if you want to save him.
This happened because you used cuprazin a.k
.a copper in your DT. Cuprazin kills your nitrifying bacteria and that is what's happened to your tank. You should never use any copper treatment in your tank, that stuff is reserved for use in QT tanks only. By using it in your main tank, your going to have ammonia problems for a while until the copper gets removed. Also as a side effect, you may never be able to keep any animals sensitive to copper in that tank. The copper absorbs into everything and will take a long time to completely leach out. Sorry to be the bearer of bad news.