I have a 12" flowerhorn that I recently relocated from his cramped 55 gallon tank into a 120 gallon. I cycled the tank and the fish has been in contact with no other fish. Water parameters have been stable. He's been in the tank for about two months.
When we moved him, we noticed he had atrophied somewhat from being in the smaller tank (we'd just moved cross-country so had limited real estate for him for a little while). We figured the 120 would help. We fed him about a dozen pieces of Cichlid Staple every day and kept an eye on him. He seemed more active and happier at first, but now he has a TERRIBLE looking lesion on his back between his dorsal and tail fins. Since moving him, his dorsal fin has been "flopped over" to the side and he principally hangs out vertically near the top of the water with part of his tail flesh sticking out. The part that he continually has sticking out of the water is what has gotten the lesion. It's to the point where it has eaten away at all the skin and scales and now there are larger veins showing. I'm getting VERY worried (well, I was pretty worried before).
I've looked through the Freshwater symptoms but nothing absolutely fits. He isn't breathing hard, there is no evidence of bacterial or fungal infection around the gills or eyes or lips, he is eating, but it looks awful and he seems like he is in some degree of pain when he swims. We've done a 30% water change, added some more salt and am thinking of bumping up his diet to something more high protein.
Does anyone have any recommendations for medications or water treatments? I am not very well versed in diseases; I've had this fish for 4 years and this is the first time he's been anything other than tip-top.
Thanks all!
When we moved him, we noticed he had atrophied somewhat from being in the smaller tank (we'd just moved cross-country so had limited real estate for him for a little while). We figured the 120 would help. We fed him about a dozen pieces of Cichlid Staple every day and kept an eye on him. He seemed more active and happier at first, but now he has a TERRIBLE looking lesion on his back between his dorsal and tail fins. Since moving him, his dorsal fin has been "flopped over" to the side and he principally hangs out vertically near the top of the water with part of his tail flesh sticking out. The part that he continually has sticking out of the water is what has gotten the lesion. It's to the point where it has eaten away at all the skin and scales and now there are larger veins showing. I'm getting VERY worried (well, I was pretty worried before).

I've looked through the Freshwater symptoms but nothing absolutely fits. He isn't breathing hard, there is no evidence of bacterial or fungal infection around the gills or eyes or lips, he is eating, but it looks awful and he seems like he is in some degree of pain when he swims. We've done a 30% water change, added some more salt and am thinking of bumping up his diet to something more high protein.
Does anyone have any recommendations for medications or water treatments? I am not very well versed in diseases; I've had this fish for 4 years and this is the first time he's been anything other than tip-top.
Thanks all!