I think this is a hard question to answer, that's why you have no responses. I switched from a Tek 8 bulb fixture to 4 Sol blues. I started at 30%or so on all colors. The corals seemed OK, perhaps a little stunned. They had minimal growth for a few weeks, and colors browned a bit on the SPS. LPS and zoos looked great. After a few weeks I gradually increased lighting and corals are colored up more and growth has taken off again. I must admit there was a few weeks that I regretted making the upgrade and thought I made a huge mistake. I am now happy with color and growth and am up to 55 or 60% on all colors. Since you are starting with a fewer bulb fixture of T5s, I would start out slow, very slow. HTH