as a general rule you should have at least 5x exchange - meaning a minimum 0f 375 gph in your case - other factors will be what kind of equipment you will be using and what type of tank you will be setting up.
actually most I know run 20 x's on fowlr and 25x's on reef so 1500gph for fowlr and 1875 on a reef. Im setting up a 75 with 1800 gph on the return line pluss a cupple power heads
