ok, here is what i did for my tank...
i got a CPR overflow, for like 65 from LFS
, and glued like, 1/2 inch PVC
to the output or what ever its called. then put a pvc
nipple on it, in which i put 3/4 inch vinyl tubing (which i also got from LFS
for like 1.00 a foot) and had it lead into my filter which dumps into my sump (i built a wet/dry trickle filter from scratch) from there i havea fairly powerful pump, which picpes the water straight up like...4 feet or so. now you asking about flow rate, i got a secret ill let you in on. over estimate the power in the pump you need, its always good to over estimate then under. i got a pump that was quite a bit more then i thought it was (and the LFS
said it would barely do the job) well when leading the vinyl tubing back into the tank, i installed a PVC
ball valve with the 3/4 inch nipples on the end (and got pipe clamps to deal with any excess pressure build up and keep it from bursting). this way i can regulate how much flow goes in and out of the tank. and on its lowest setting, it can turn the tank over in like half an hour. where its set right now its turning the tank over like, every 20 mins or so. and i have a 35 gallon.
anyways, for flow, just install a ball valve and regulate it. typically just slapping a power head with no regulation control is a bad idea...cause your stuck at one setting, which can be to strong, to weak, or absolutely perfect. either way, its good to have a good return pump in there. i think i spent maybe 30 bucks on mine.