Reeflady is right
I have been reading up a lot on diatom blooms and stuff and althought my crabs, snails and Blenny make short work of it, it is a good idea to check those levels and also use an RO
unit for your make up water from what I have been reading. Every time I use my well water to make up or top off, it seems like the bloom rears it's head a little for me.
My tank has just finished initial cycling, a couple months old or 3, soooo.. aha... maybe my well water has bunch of silicates or something in it. Time for me to try an RO
unit as a first step and go from there. also here is one of the links I was reading. http://saltaquarium.about.com/b/a/001466.htm
Thanks and peace