Overdriving a T5 is not necessary if you buy a good fixture with good reflectors. ATI is one of the best and there are two tanks on R.C. that have won TOTM using this fixture. Every day people are making the switch from 400W M.H. to a high output T5 fixture and are reporting they're "bleaching" their sps corals because they didn't properly acclimate to the new light. Until you see for yourself how powerful a good T5 fixture is, it's hard to believe. I'm personally experiencing how many benefits of T5 lighting and so are my corals.