Diatoms - How Long after new sand?

[usfpaul82]

Hey all. I have a well established tank, several years old. About a month ago I put down a new layer of sand. I used caribsea dry and I rinsed it very well. I figured I would get a diatom bloom, but nothing until a few days ago where now I have a nasty diatom outbreak all over the sand. Is it normal for the diatom bloom to take nearly a month to happen? I figured it would have started earlier. I’m just trying to figure out if the bloom is due to the new sand or something else possibly.

 

[lapin]

I added 3 big dry marco rocks to my tank. It has taken about 1 month for them to show the brown spots. My guess is 30 days is not out of line.