Well, I've got a real small Hydor mini in there right now. 7.5 watts. It keeps it a little cooler than it should be in the winter, but now it's doing a good job. I expect it to be a little warmer in the summer. As far as water changes go I started out doing 1 gallon changes about every month, but recently I've been doing about 2 cups a week to keep everything more consistent in preparation for the new arrivals. I top off about every three days. There's not that much evaporation now, but I expect it to go up with the new lighting.