I would definitely go with 2, worth the money to not have a shadow in the middle IMO. I have 2 250w on my 55 and it is bright everywhere in the tank. Be prepared to deal with heat and evaporation. My tank would go up a degree an hour when I first turned mine on. I cut vents on either end of the tank and mounting 2 110 watt fans on one of the vents and it seems to have taken care of the problem. I also lose close to a gallon a day due to evaporation. This is totally off topic, but just wanted to give you a heads up if you didn't know. As for the questions, we love em, gives us saltwater geeks something to do! _________ 55 gallon reef aquarium, 85 lbs. live rock, 2 1/2" sandbed, False Percula Clown, Foxface, Whitecheek Tang, Tetratec PF500 filter, 2 110 watt URI Super Actinic VHO actinics, 2 250 watt metal halides with Reef Optix 2 reflectors powered by Blue Wave 3 ballast Born 1/3/08 CHECK OUT: My Tank Thread My Tank Video My 2nd Tank Video | 
