Review on YukiHalu Small Size Submersible Aquarium Heater: Accurate 1℉, Mini Fish Tank Heater 50W 100W with Thermometer & LED Display by Michelle Hall

I used this to heat a hydroponics tank and found it was 6° overheating the tank. I tested with two other thermometers and an Atlas Scientific temperature probe. When this heater said my tank was 68°F, it was actually 74°F. Now I set this thing to its lowest temp (64°F) so it will maintain a 70°F temperature in the tank. Looks like I'd hook it up to a power relay controlled by my Raspberry Pi and let it maintain the temperature instead of relying on that heater to control the temperature.