Weird! We have one too that we raised from a baby, a dalmation lyretail. He sometimes sits near the bottom and wiggles without going anywhere, and sometimes does like yours and sits near the heater. Then other times he is very active zipping around the tank and he has no feeding issues. Now I have seen both those as signs of illness but this has been going on for months, no new fish added, and very stable tank. I noticed I never see him raise is top fin, ever, and when he swims his side fins kind of point upward and make circular motions. I am wondering if he even has a top fin. He has a ridge there where there should be one but with his odd way of swimming I am wondering if he has one.
