I have a large granulated catfish(pterdoras granulosus) at about 28 inches. My experience with my fish it that they do not like warm temperatures and mine would barely eat at a temp of 77 degrees. What I found out when one of my heaters gave out is that he thrives at 73- 74 degrees though. Something for those to try if they're having trouble getting them settled in. I didn't expect a few degrees to make difference but it is night and day for my fish. Be careful though, other big cats, especially rtc, prefer it a bit warmer imo.
That is something I will have to keep my eye on. With my bass I am keeping my water at 81. Ill observe him over the next couple days and see how it goes. Since I have gotten home from dinner he seems to like to hide behind the heater. Could this burn him? I figure if it was hurting him he would move but what if he does it while it is on. It is a 300 watt and is on pretty frequently. I would also love to see a pic of yours, I would really love to see what I can expect him to look like in the future.