Brown spot on sand?

[ChangDriX]

I dunno if it's diatoms, but this just appeared out of nowhere.

thanks :help:

 

[vorlx]

Looks like diatoms to me. When my tank was cycling I had a nice outbreak right towards the end. Covered alot of my sand bed for awhile.

How long has your tank been cycling?

 

[Reefscape]

yep, certainly agree that you have a diatom bloom starting there..Am i right in saying this has not long fisnish its cycle?

Niko