Depending of what type of light appeals to you. You can be safe with 2 150
MHs and 2 96w
PC for atinics. If you like the real blue look you can have 20k
MH and
Actinics, or if your looking for growth then 10k with
actinics. If hou didn't carefor
metal halides then go with
T5s and alternate the 10ks with the
actinics, but have had no experience with them. I had gotten away with
PC over a 55gal before, but the more I added I began to struggle with the temp. Plus, the tank isn't that deep so you don't want to cover the whole top with lights do you? I personally would go with
MH and
PC combination if I were to do a 55, infact I may just turn my old 55gal into a
frag tank.