Growth on rock

[Lexigirl]

Can someone identify what is growing on my rock? It is rust/brown color. Tank is about 7 months old. Thanks!!!

 

[Gregcoyote]

Can someone identify what is growing on my rock? It is rust/brown color. Tank is about 7 months old. Thanks!!!

It's called cyanobacteria if it looks like a coat of red paint. It can be removed when it forms by siphon or net. It is common in new tanks (7 months is still new) and forms in low current areas as a result of phosphates being too high.
Water exchange, adjust power heads to add flow and the stuff will disappear.

 

[Lobstercrazy]

If it is browner it could be diatoms.