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 Drew Serrano

I first bought this heater for my 2.5 gallon Betta aquarium. He kept the water temperature between 30 and 30 degrees, which is too warm for the bettas. The thermometer I had there actually went up to 83.5 so I was worried about leaving it unattended because it doesn't always stop heating at 82 like the description says. Since then I've put the fish and this heater in a 5 gallon tank and the water has stayed at 78.6 which is near perfect. I think this heater is too hot for a small tank and I definitely recommend checking the temp frequently if you have one in a smaller tank. I use both a thermometer and a digital thermometer and check them several times a day to be on the safe side.