Does anyone run 400's on a 120? Any heat issues? What ballast and bulb? I have been given two 400w magnetic-standard ballasts and was thinking about using them instead of my 250's. Heat is a concern of mine. Any thoughts?
Yes... you will have heat issues. Period. I dont think you can get away with not running a chiller with 400 watters. FOr a 120, I would stick with what you have... or maybe add a third 250w (thats what I did). GL!
One 400 on a light-mover on my tank. Icecap electronic, lumenarc, and 20k xm. The corals are responding well to the mover, and reduced shadowed areas. Ambient temp in the house is 75 or so, and tank stays at 80. Light is about 10 inches above the water with 7 hour photoperiod. The only issue I might have is too much light intensity, maybe.
The heat issue depends alot on how you are mounting your light too. Most people who have a heat issue with MH usually employ an enclosed hood design of some sort with inadequate air circulation.
With an open top design the heat is significantly less of an issue.
That said, I also think you should stick with your 250Ws the 400Ws aren't needed on a 120g.