I have a tank at 400 gals and use a choked hammerhead for return most likely about 4000 gph and 2 dart pumps about 4000 each attached to ocean motion 4 ways for closed loop. It was not enough. I added 2 3000 gph powerheads. It could still be a bit more. If I were you a may just consider using 2 large vortex pumps. I think they make a 7000 gph, it is really a lot less plumbing and possible leaks. If you want to look at my tank email me eralff@comcast.net, I live in Newtown pa about 1 hr from you.
300 gallon (sps reef)
1 - Hammerhead chocked down through 2 seaswirls as return
5 - Tunze 6205's with multi controller
180 Gallon.
4 x MP40s, long pulse, full blast non synched.
2 x 3/4 in. sea swirls on the returns pushing about 1200 gph total.
4 x Modded Tunze Nano 6025
2 x 6055
1 x modded 6045.
Needless to say, bare bottom. Very chaotic, with tunzes blasting into the mp40 streams and the sea swirl breaking things up.
Herb
are you using the tunze multi controller or controlling thru an apex like controller?