I have heard that growth with the 12k's is slow. With my 10ks I am running them without actinic supplementation and everything looks great. I do not have any brown polyps on my blue corals. The blues are blue. I was concerned about changing from the XM's with great growth to these reeflux but that is not an issue. My growth is easily as good as with the XM's. And the color is way better.