This heater comes in 3 different sizes, 50w, 100w and 200w. All are the same brand and are quality products built to last. In my experience, I find that all measures such as keeping the lid on tanks and having the tank filled to an adequate level of heat will be retained easier and I can safely say that for every 1l of water you have you should have a 1w heater. For example 50w = 45L-50L. 100w = 95L-100L. 200w + 195L-200L. So on and so on.
