Brian (lazylivin) you are the man. I was always told you could not run a 400w bulb on a 250w ballast because it would not fire. Brian said his tank is being ran with 400w bulbs ran at 250w, so I tried it. I pulled out an old 400w blueline bulb and hooked it to my 250w ballast and wow, it looks good. I would assume that a 250w bulb would also work on a 175w ballast.