Its going to depend on the zoa (and your individual tank and conditions)...for example AOG, my bam bams, radio active greens and TRPE love high light T5s while my lunars, KO nightmares, blue smurfs, etc would rather be in lower light....when I frag stuff I try to experiment and put one of the in bright and the other in moderate light and monitor growth..kinda fun!! Whee!