part of the answer will lie in you rockwork placement. In the end you don't want any crap to settle on the bed of you tank or in any corners, but you also don't want your lps to get blown around and hence not open fully. With the powerheads you have currently you can place them in your tank and then see the effect on the lps. If you find certain spots in the tank are not getting enough flow you can then add more. In my tank I've got sps as well as torches, frogspawn, gsp, Xenias, Shrooms, flowerpot, and some zoas, and my flow can get up to 48x turnover with no problems. It just came down to rock and coral placement in relation to ph flow angles.
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RSM 250. Clownfish, Fox face, Blue tang, Yellow tang, Kole tang, Clown tang, Coral beauty angel, French Angel, splendid dottyback. CUC, softies, lps, sps.
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