At least I think it’s hair algae? I have Astrea snails and trochus snails but they don’t touch it. It’s on the main rock piece in my tank. I sometimes lift my strawberry conch up there to eat it but I’m not sure if he does actually eat it. It’s not fast growing but there are more patches of it. Looks brown in the tank but green under natural light. Growing like pieces of moss but also some wirey stalks.