Review on Aquarium Heater with External Temperature Controller, LED Display for Marine & Fresh Water - Submersible Fish Tank Heater (30-180 Gallon) by Jennifer Middleton

Although the product heats up the tank quickly, the refraction of light in the water makes the display difficult to read when installed in the tank. Additionally, most people run their wiring behind or under the tank and trying to install this is futile. Although it displays + and - to increase and decrease the temperature, for some reason it will start over if you stop, and since I couldn't see the display and adjust it at the same time, I had to rely on someone to tell me more about that Numbers, and until we figure it out, it all starts all over again.