I have a 6 bulb fixture and run 2 aquablue special, 2 blue +, and the other two I've been playing with. I had an ati actinic which I wasn't crazy about. I'm using a fugi purple now that I really like. I've also had an ati pro color, which is a red bulb, and a geisman 6k, which is really yellow. I would go with 2 aquablue specials, they aren't really blue, more of a white bulb. and either two blue plus, or a blue plus and a figi purple. ask 100 people what bulb to use and you'll get 200 answers. it's already been said, but t5s are relatively cheap to replace so if you don't like what you have, try something new. maybe there is a local reef club that you could join and borrow a couple bulbs and really experiment.