The tank has been set up for 1 year, I don't beleave that it is diatom algee, this is thicker and clumps the sand together. I get the di from my lfs, I have tested the tank for phosphates with two different test kits and they both read 0. As for the nitrogen gas this happened after the tank was set up a couple months, I don't know why it is happening again, that is the part that has me pulling my hair out. Any more ideas. thanks