What algae is this and what causes it

[Gustavo Gruner]

Hello everyone,

I’ve been having problems with this algae for a long time. It always grows in the same place (on top of some specific corals). I

brush it off using a toothbrush, but it grows back again.

What type of algae is this? And what usually causes it to grow?

 

[RedReefer]

Green hair algae. Usually caused by water quality issues.

 

[Gustavo Gruner]

 

[Gustavo Gruner]

Green hair algae. Usually caused by water quality issues.

What kind of water quality issue? Any specific element? I have a 4-stage RO/DI system, and I replace the filters every year.