I'm running a hydor koralia #3 right now. I have a #2 also, but it's out at the moment while I'm experimenting with positioning and aiming them. I'm probably going to keep both a #2 and a #3 going in order to keep the water surface agitated and to discourage algae from growing on the rocks and sandbed. Using both at the same time does seem to raise the water temperature a couple degrees. _________  |