How big of a pump do I need?

[hookedonfish]

I am making a sump for my fish tank and want to know how big of a return pump I need. The drain hole consist of a 1 3/4 size bulk head, I believe the drain hose is 1 inch. And I believe the return hose is 7/16. The sump is about 3 ft below the tank. I am debating on some pumps but dont know how much GPH I need. Any input would be great!

[Geoff]

a 1" drain will handle just shy of 600gph. so you wane to keep the max below that for that amount of head height. the closer you get to the maximum the greater the risk of something going wrong. i would prolly stick close the 400-500gph range for that head height. something like a mag 5 would be good.

the return size is pretty much irrelevent. you can pump a lot more water actively through a given sized tube than if it were to be gravity driven.

G~