Review on Energy-efficient Betta Heater for Small (1.5 gal.) Tanks - Fully Submersible Aquarium Heater – Automatically Reaches Preset Temperature – Easy Installation with Suction Cups by Maria Miller

I have to say that this is not what I expected when I bought this heater. I put it in the tank today because it was supposed to be cold after I went to work. I watched him for a few hours and everything looked fine. Well I just got home from work. The tank was full of steam, I felt heat outside the tank, the betta that was in the tank died. Couldn't figure out why. That was until I opened the lid. Nothing but boiling heat came out of the tank and the water was incredibly hot. The heater had clearly passed the 82° mark it should have turned off and I lost my fish in the process. Wouldn't recommend it.