I have two 175's and 4 440 of vho in a 110 18" high, 60" long (the frag came from a 125 with 3 175's mh) I am thinking of buying a third 175 mh to mount in the middle. I have put it about mid way up the tank, with the option to move it up to the top. I have had the system up for 19 months now. Wet-Dry system, sea clone 150. Water's fine ca at 450. Haven't had anything die in the last 12 months except for the two hard corals.