You need a return pump that is rated for 600gph or less at 5 feet of head height. You then want a couple of power heads inside the tank to increase the flow within the tank.
Is your refugium actually a sump sitting under the tank or is it a hang on back or other true refugium?
Do you have a protein skimmer?
How much live rock do you have?
You want to create a chaotic water flow through the tank so you have areas of higher flow and areas of lwoer flow. Some corals need high flow, some need low flow.
Have a look at Melev's site
for sump/refugium answers