10k doesn't mean to much. One 10k bulb will be ok and another will be great. Coral life is what a lot of people use when they are talking about 10k and i think there a pro choice. I use Custom sealife myself but i use 8800k and just broke that so now i will try their 10k. But 8800k CSL beat the heck out of 6500k CSL. I've enver had worse growth than with CSL 6500k. the 8800k had my plants pearling even at under 2wpg.