Any help is great

[Ag6594]

This has been on my rocks for about a week. Tank is about 3 weeks old so I'm hoping just diatoms but not sure.

Any advice is appreciated.

 

[myinvalidname]

Looks like you could have three different algae and bacteria. There is some hair algae. Possible some diatoms underneath what looks like cyano. The cyano should blow off easily with a baster, if it hasn’t matted yet. The diatoms are the golden brown powder. Diatoms will go away by themselves. The cyano could be developing in a low flow area, which changing flow directions or increasing flow could help. Some snails and hermits can keep the GHA down.