Contemplating a switch to T5's

[Myka]

What type of clam? You may have troubles keeping a Crocea or Maxima in a tank with Zoas and Acans since the latter two are relatively low light corals (or they will bleach out), and Crocea and Maxima are both high light clams. Although a Crocea would be a good choice for your tank since it stays smaller. Both Squamosa and Derasa would be good choices for a 4-bulb T5 fixture, but they both get big. Zoas and Acans would probably get too much light from a 6-bulb fixture imo. When I had a 2x39w T5 fixture on my standard 33g tank my Acans and Blastos wanted to be near the sand, but of course the 39w bulbs are significantly stronger than 24w.