Well, I can't find a test for silica anywhere here, so I will have to try to get one online. But, I added the rocks, 25 lbs to a 125, really only change to the tank, and within two days diatom bloom. Got a phosphate/silica sponge, and it seems to start going away today. But, yeah, considering the fast bloom, and it being an only change, I would have to say yes. i got the Key Largo rocks. Once I get the test, I will keep you updated. I really doubt its the bulbs, they are less than 5 month old ATIs.