Review on Hygger Digital Temperature Controller Aquarium Heater - Shatterproof Titanium Tube, Submersible Fish Tank Heater for 60-180 Gallon Tanks, 500W 800W Power - Ideal for Saltwater and Freshwater by Carla Martinez

My 30 gallon reef tank is set at 81.0* and won't start until the tank drops to 80.0* and then shuts off when it goes back to 81.0 * is heated, but then the temperature continues to rise to 82.4* (due to residual heat in the heater), then slowly drops to 80.0* before turning back on. Not very happy with the temperature difference (2.4*) this heater creates. I have it in the divine flow realm too.