Any idea what this is?

[johnson528]

The whole sand bed was white and clean just yesterday, now these brown spots are appearing all over the bottom of my aquarium. I seem to be missing a fish, but I haven't moved live rock to check yet... I have no idea what this is, help! Thanks!

[mcgyvr]

No pic but probbably diatoms..
I assume this is a new tank and as such diatoms would be normal.
Just part of the stages of a new tank..

[Stevenliu9]

No pic but probbably diatoms..
I assume this is a new tank and as such diatoms would be normal.
Just part of the stages of a new tank..

Yes, and if you are missing a fish, assuming it is dead and stuck somewhere it would be the culprit of the spiked nitrate to cause the diatom.

[vanbro1]

Diatom