I have been thinking of running 2 smaller submersibles, or one larger one. The pump Sam had mentioned looks very interesting and only drawing 40 watts there should not be much heat transfer either. I had to throttle the dart way back as my overflows couldn't even come close to keeping up with it and it was older, so maybe that was why it was noisy. After what happened with my last external pump I think I will stick with submersibles for a while.