What disease is fatigue characteristic of in a fish?
As others have said, I may first consider water quality…if not ammonia poisoning, what about your nitrites and nitrates? Fatigue can be characteristic of a lot of things. Lethargic behavior (or else on the other end of the spectrum, erratic behavior) is common with most fish diseases, so you really can’t narrow it down for now, not until you are able to see any other visible signs of disease. You should familiarize yourself with what those things are, i.e. tiny white spots, fungus at the mouth, tails tattered, protruding eye or bloating, and so on….so that if other symptoms show up, you know what it is and are ready to get to treating it. One thing it could be, if you never see other visible symptoms, is an internal parasite just eating away at him…and that will inevitable kill him eventually, if you don’t treat for it. So give it a little time, and if you still don’t see anything, I’d maybe treat for internal parasites. In the meantime, I would add aeration (like with an airston
