From what I have heard, you can not have too much water flow. I run 2 power sweep 214's in my 29 and have a fluval 304, along with a cpr style skimmer, not exactly sure how much flow, but I am thinking I have about 650-700 GPH in there and if you want to do any reefing chaotic flow s best, not just the same direction
The Powersweeps are nice because they rotate back and forth and are only 20-30 bucks!