My opinion is, as long as the tank looks healthy, then it is. I've had my biocube spike at 83* before, and it regularly sits between 80 and 82 degrees. I have LEDs, but I have a lot of stuff in the back sump, which is what's probably heating it up so much. But my tank is super healthy, and everything is growing very rapidly. So I'm not concerned about it. Occasionally all my snails will be towards the top of the tank, and that's usually when it's kind of on the hot side, but they're the only ones that seem to mind, and they haven't been doing it for the past month or two, so I think they've gotten used to the temps I keep the tank at.