You can dim them, they just have to start at 19%. I had 3 blue daylights, blue pop, biotek marine 20k/uv, and a biotek marine 10k/pink installed on my ATI 6 bulb fixture and did par tests yesterday after noticing a few of my sps mid column starting to RTN at their base. I got 172 6" below at the surface. This explains why my sps lower in the column have been stressing. Good for supplemental bulbs, but I don't recommend running all of them together in an sps tank. Better to mix and match with T5's.