to answer your original question, 3700GPH + 660GPH return from sump (36x / hour). I think 12.5x is perfectly fine, if not a bit low.. but with MJ's, try to point them at the glass or use the diffusers to prevent a "stream" of water..
Bubbles in a SW
tank can serve their purpose if you have overflows. I read this on another site, seems to be working great for the person doing it in a 240Gal, not personal experience.
His explanation which makes sense: By periodically blasting air bubbles through your tank you turn it into a giant protein skimmer (as mentioned above by Ziggy), the dissolved organics will attach to the bubbles and float up out of the column, onto the surface and into the overflow where the skimmer can take care of them.
This should not be done for more then 1 minute at a time and I think he mentioned he does it twice a day, also be careful with corals, they will slime up with contact to air.
120 Gal SW, 150lbs Prem. Fiji, 23Gal Sump, 2x250w 15K MH, 4x65w Actinic
3 x Halichoeres Chrysus (1 surfed), 3 x Nemateleotris magnifica, 1 x Centropyge bicolor, 11 x Scarlet Hermits, 6 x Zebra Hermits, 40 x Astrea Snails, 6 x Nassarius Snails, 3 x Cerith Snails