I was reading on a horticulture websight the other day that someone had takend a HPS ballast and wired it up to run a MH bulb. They didn't give any specifics on how they did it. I was wondering if anyone out there has any experience doing this because i was going to build a MH canopy for my tank. I already have a HPS ballast but if it to hard or not very safe then i dont want to. I will just get a MH retrofit kit and do it that way. I was just thinking i could save a little money if this is possible.