a friend of mine has a 29 gal. He has 2 MJ 600's, the return from his cannister filter and CPR-Bak Pak skimmer. He thinks he gets good flow. If it were mine, I would have to at least try a MJ 900 and work my way down.
rule of thumb here i prefer a 20X GPH turnover, i have a 75 gallon FOWLR set up and i have 1245 gph so i have a 20.58 turnover(i figure 60 gallons of actual water after substrate and rock) but its neccessary for a FOWLR set up but why not? its crucial to have a 20X turnover in a reef system. some say 15x for a FOWLR but it works for me