Noticed one if my tanks was a few of degrees higher than usual a couple of days ago. Didn’t think that much of it as it’s warming up around here but we haven’t used the AC yet. Usually keep tanks 76-78. Went to do water changes today and as soon as I touched the water I knew that same tank was way high. It was 93. Pulled heater out right away and it was very warm. Got temp down with slow water changes to about 83. Leaving lid off and turned the overhead fan on to cool the rest if the way. Fish seem ok. Guppies, lamb chop rasboras, and plecos. It was an Aqueon Pro 150 watt heater about two years old. Glad I caught it in time. Threw a 50 watt heater I had in there for now until I get another one.