I would go with 4 bulb fixture. You will get better growth in your macros and corals. On bulbs, a 1/2 and 1/2 will give a pretty intense blue light. You might consider a mix like one actinic, one 12k, one 10k and a 6500. Just depend on what your looking for. The nice thing is at $15-20 buck a bulb you can kind of mix and match pretty easy. Dr Foster carries T5s along with http://www.innovativelights.com/. I have bought T5s from bought places with no problems