Review on 🐠 Adjustable HITOP Submersible Aquarium Heater: 100W/200W/300W/400W/500W, Suitable for Large Fish Tanks up to 150 Gallons, Includes Sturdy Protective Cover and Thermometer for Optimal Performance by Marcia Wilson

When I received this heater it was used. When I placed it in my fish tank and set the temperature, it quickly heated the water but didn't stop at the set temperature, instead continuing to rise until it fried the fish in the tank. To stop it from rising I had to lower the temp and at that point it would no longer turn on to heat when the water temp eventually dropped, I would have to do it manually by raising the temp again. Basically, it looks like the thermostat inside the unit has failed. So I wrapped it up and sent the piece of junk back. I do not recommend this item at all. The maker of this product should be ashamed of selling such rubbish and Revain shouldn't be stocking it, shame on you!