Diatoms or something else

[Nick92515]

Trying to figure out what this brown stuff is, it's not a mat or hair, looks like diatoms but not sure.
Tank is 5 months old, rodi water with 0 tds. Light biology with 3 fish in the 55. Also have a variety of snails and a fighting conch. Currently battling some cyano as you can see but I don't think that's why all of the sand is brown. Phos test shows zero but I know I have some since I have algae.

 

[thegrun]

The pictures are not real clear, but yes it looks like simple diatoms to me. Increased flow may help but they often go away on their own as your tank matures.

 

[Steve175]

I too would rec increased flow