Cyano against glass

[Jon T4S]

Hi, I have a small 13.5G Reef tank, recently I noticed cyano bacteria(red) up against the glass. It disappears when disturbed, but is right back there again in a few hours.

It is nowhere else in the tank, so I wonder should I leave it? or is there something I can do?

Thanks!

 

[Uncle99]

Increase flow in that area if possible.
If it persists, than check to see if your N or P has bottomed out.
If either or both have, increase back to “normal” levels.