Hello,
Tank circulation like many variables (ie. temp., calcium, lighting hours, water changes, etc.) are highly debated. You'll hear many say there should be 5-10 changes per hour (5-10 times the volume of the tank of circulation per hour, counting all powerheads, and overflow).
Others would say you need 15-20 changes...
Some say random motion is more important than total volume, while others would say you can't live without wavemakers.
For me, I always try to recreate ocean conditions...or at least as much as my pockets can afford. But even than, you have to ask yourself what part of the reef you're trying to recreate? A shallow lagoon, a barrier reef, a deep cliff side, etc...
You have to keep in mind the type of animals you're planning to have. SPS and anenomes require a lot of current...but softies and LPS actually prefer medium current.
I keep primarily SPS now, thus I prefer a lot of current.
I use one return pump feeding my Seaswirl (1000 gph), one 400 gph ph on one corner, and a 700 gph in the other corner in my 75 gal tank. My sps and fish love it...
On a side note, I'm also trying another powerhead that uses a propeller. You can find it at
www.reeftec.com
It creates a much larger cross section current as opposed to the traditional powerheads.
Regards,
Terrance