You might want to consider investing in a submersible heater. That is known to happen with the hang on heaters, especially if there has been any evaporation. There is a water line that should be marked on a hang on heater, and if the water level falls below that line, then all sorts of problems can develop, higher temp is only one. Those heaters are known for breaking if the water line goes down too far, and I stopped using them years ago because I found them to be unsafe for me and my fish.
Considering the animals in that tank, and looking at your pics (nice pics btw), I will still say you need a much larger tank asap, and you'll want to add more decorations in the meantime, too. I'd suggest more small/short plants and maybe a piece of driftwood for the pleco.
What you have done here is to start a tank of all bottom feeders, which means more competion for food and for territory in fish that are not well mixed in that size of a tank. When that shark starts to feel crowded, I fear he will attack the corys, and waste is going to build as he gets bigger. Redtail sharks top out at 6 - 8 inches long and can be very aggressive. You haven't allowed any space for the fish to grow, so once growth spurts begin, you're going to run into all sorts of headaches.
Thanks for all the advice. Like i said awhile a go check the diy forums cause i might be building a tank. Also that heater was submersible, it had a minimum water line and i had it about an inch above that at all times. I think what happened was the knob broke and kept the temp going higher. I'll be sure to ask for advice when i build my tank ( what fish to go in what).
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