What's this red stringy stuff?

[jennowensucd]

Anyone know what the red hair like stuff is on this rock?

 

[Sniperhank]

Cyanobacteria. Feeds off of nutrients in the water column like algae does, but thrives in low flow areas.

 

[jennowensucd]

Thanks!

 

[54seaweed]

large water changes siphon out as much as you can with water change , add more flow to cover any dead spots