I'd do one mp40. My bro in law has a single mp10 on his 40b, and it works well enough but is a bit loud at the higher rpm range, and he's got all soft/Lps corals. With a mp40 he would have better flow and less noise.
I'd also go mp40 as one will do teh job cranked down a bit and better expandibility of you decide to go bigger one day
Like running two mp40's on a 60g cube, then later upgrading to a 180g ? ;-) and everyone called me crazy, not crazy just thinking ahead, lol
I never called you crazy, I just thought it
They sure were quiet on that old tank!
Your right, I think it was Dan that actually said it.