There are a few factors that go into the rating of your return. What your sump is rated to handle in gph (since yours is diy you'll have to wing it), also what the total flow and turnover you want for your tank to be. Return plus all power heads. Then, do you want to run any media reactors, or uv sterilizer? If so you'll want to add gph to your return to account for any (or all) of those. Ime I would like to get a higher rated return, so I wouldn't have to use so many maxi jets. Additionally, you can always split or aim a return differently, but you can never add more power too one. Check out the controllable dc pumps