My 24x18x18 has mainly zoos. I have been lighting it with one 175W MH, however, I am not happy with that, as some of my zoos are doing less than perfect. I have changed to one 24W T5 daylight, and one 28W actinic PC. To my eyes the zoos are doing better. I have ordered a 65W 460/420 nm bulb, so when it gets here I am going to give my 2X65W PC fixture another go.
My preliminary advice is then "don't use halides in a tank that size if you are doing mainly zoanthids"
