I ask because i want to get a 6' long 2' deep and and no taller than 2'.I fear if i get a taller tank i will have to upgrade to 400w MH's when i already have 250w. I dont want to spend more money on a custom tank or upgrade lights.I may however end up getting 1 400w to place in the center of tank.I'm still am kicking around ideas. I plan on haveing a SPS dominant tank.