I have a 72 bowfront up and running for about a year. Have a variety of inverts/SPS/LPS/Reef friendly fish. I was previously running T5s but decided last week to spring for a metal halide fixture. I purchased a new 150w x 2 HQIs with 4 x 54w blue T5 actinics/14 watts of moonlight closed light fixture off of ebay. The description looked great and the feedback was great. After unpacking it and mounting it atop my tank i noticed a lot of heat. I also noticed the lack of a fan. The fixture did have a lot of vents for heat escape. After two days of running it only 5 hours per day it raised my tank temp 10 degrees!!!! Question is this, if I add a fan will it help and how much? Am I gonna now need a chiller? The tank is in my office where the temp stays pretty consistently at 67 - 70 degrees all year. Please some advise, I'm starting to think my T5s were pretty good after all.