So for most tropical fish you will normally need a pre-installed heater that will keep the temperature around 22-30°C. This heater typically heated the tanks I tested (3 gallon and 5 gallon) to 82°F, which is a little hot. I took this heater in for cleaning when I was cleaning my tank. After a while I noticed a strange smell and realized that this heater was still connected to the mains. It's a common silly mistake, but good heaters can detect when they're overheating or run out of water and shut down safely. This heater just burned out. He melted the foam he was leaning on, then softened the outer plastic to the point where it became flexible. It burned when touched. If he had been in an aquarium, he would have killed the fish. I had to run it under cold water for a few minutes until it cooled enough to throw away. I strongly recommend not buying it. Buy a heater with an adjustable thermostat. They are bigger but safer. Aqueon - the manufacturer of this heater - sells reliable control heaters. I'm not sure why they would sell this junk. It hurts their brand.
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