Check the manual and and see what the reccommended flow rates are, then size your powerhead accordingly. We ran one for a a while and just had it taking it's source water from the sump and the output weent into the the refuge(it was a 3' unit)... but dumping back into a high-flow area of the sump would be just as good. For dependability I'd use something like a MaxiJet, they seem almost bullet-proof.