Hi. I used a Kessil A150w 10k over a 29g tank for a year. A note- Kessil bulbs seem to run a little bluer than they're labelled. a 10k looks like a 12k, a 15k looks like an 18k, and their 20k looks like Windex lol. Anyway, the 10k Kessil gave me decent growth on most of my SPS, and also made a Tridacna clam happy. One downside to the Kessil in my tank (and I've not heard of anyone else mentioning this problem) is that, as it is a spotlamp, 50% of a branching coral is always outside of the light. Now that I have MH lighting on a bigger tank, my SPS corals have full coloration on all sides.