You are going to need more than 200 watts to heat that much water. Dont forget you have to account for the water in your sump. Assuming that you have 20 gal of water in your sump, that would give you 95 gallons of water. To properly heat your water, you need 5 watts per gallon, that gives you nearly 500 watts. I would recommend 2-250 watt heaters. I say 2 because if one malfunctions, you still have the other to keep the water somewhat warm. That brings me to another topic. The Won Brothers heater are notorious for the controlers to malfunction. I had 2 of them go bad, one of them stayed on and the other wouldnt go on. I came down one morning to find the one had stuck on and heated my water to 9.6 degrees. I lost quite a few corals, shrimp and fish. The heating rod itself is great, its just the controllers that go bad.