I have a 20g high tank with about 1600gph flowing in it and everything is doing great. I have everything under the sun in there, SPS, Lps, Softy's, Z's &P's and they love the flow which is approx 80 times turnover.
I generally shoot for 50 to 100 times turnover and in your case that would be between 1250 and 2500 gph.