I normally like to provide good quotes and sources but I'm a little on the swamped side at the moment so I apologize in advance for the poor form of my post. The answer is.....Yes, most certainly. Google "Coral Photoinhibition". All SPS require MH's right??? Nope. Google "Coral Reef Zonation". Sometimes people nuke their brand new SPS by not knowing where it normally lives in the wild. A SPS coral that normally lives 60 foot down on the deep forereef or the deep leeward side of a reef won't particularly care for a 400 Watt MH. FOOTNOTE: If someone could PM me after the Christmas season as a reminder to have me put up a decent post, I would greatly appreciate it. PS....Google Dana Riddle too. He's a freakin' genius at photoinhibition.