I have the same fixture, in 24". I used two Aquablue, one Blue+ and one Purple+, all ATI bulbs. Had that going for a little over 3 weeks until I picked up one of those extra LED fixtures Gus had for sale. Absolutely LOVE the color, but even being ATI, my 24" tall cube made it obvious how little light was still making it down into the tank. ALL of my corals are much happier now with the new LED and Im not even back up to a full light cycle yet!