I recently added a frag tank to my system as well, I am using 175w pendant with 12K which is hanging about 12" above the water level. I have PC 4" fan blowing the hot air out but at same time I have chiller in my system as well. One of the member drilled my tank (1") for plumbing and I have one MJ1200 for flow. I might take MJ1200 out and put HK2 b/c MJ has too much flow. I created 2 layer rack with egg crate so I can move my sps's on the top layer and softies on the bottom. I am using Mag36 as my return which also feeds my chiller and frag tank.
I am planning to switch the MH bulb to 15000K since my tank is only 15" high