Brown growth. Is it algae?

[HowieB]

Hi all, what exactly is the brown dust that forms on the glass and sometimes on the sand? I have no green algae in the tank, only this brown stuff. Is it a form of algae? Thanks

[ska d]

Most likely diatom algae. It usually happens in newer tanks or after changing sand beds. Silica seems to be what causes it, although I guees a build of of other nutrients doesn't help. If its a fairly new tank then once the silica is depleted it should clear up. I also find when my ro filters start getting dirty I'll get a diatom bloom. I'll change filters and everything will be nice for about 4 months and it starts crêping back slowly.