I have 3 different HiTauing Aquarium Heaters. Bought on Amazon, used for about 6 months.

2 - 100 Watt for 10-20 gallon tanks ($10 each)

1 - 300 Watt for 40-75 gallon tanks ($20)

1 - 200 Watt for 20-40 gallon tanks ($20)