I've been relying on a succession of different powerheads to supplement the flow from my sump return. I find that from the time I first set up my reef some three years ago, I've just kept on adding and or changing the powerheads to increase the flow. I guess I did that in slow increments, thinking each time, that "a little more" would benefit the reef. But, it's been clear that each time I did increase the flow, more was, indeed, better. I've read quite a bit about flow and the "need" for it with this kind of coral, or the preference for "less" by that kind of coral...but, I've found that almost invariably, the more I added the better the response from just about every kind of coral I have. That includes soft coral, LPS and SPS.
To answer the question though, the flow that I have now in the tank is coming from the returns from the sump that are on each side of the back of the tank, two MJ1200 mods and a MJ12 with a Hydor Flow Deflector on it. That gives me a total of just about 34 times the 120 gallons of the tank. I have one Mod on each side of the tank and the MJ with the Hydor on one side next to the Mod there. Surprisingly, even though the MJ with the Hydor only generates maybe 250gph, it has the effect of creating a randomness in the water movement that's very natural and I think benefits the tank overall.
