This marineland submersible heater has put in work and continues to go strong. My quarantine tank is in my basement so this time of year I wrap hoodies around my canister filter under the tank and cover the top of the aquarium with a towel. It’s their smallest heater, for a 20 gallon tank. Before I insulted the aquarium the heater ran 24/7 and kept my water at a nice 81 degrees. (had it set at 82f) This tank doesn’t always have fish in it so I felt no need to buy an extra or more expensive heater. Great job marineland!