What is this

[r4rlee]

What is this it Appeared overnight on one rock and the shell of snail

 

[Cell]

Bubble algae. It didnt just appear overnight though, you probably just overlooked it.

 

[Sharkbait19]

Agree bubble algae, probably always there, just now noticing how bad it is. It doesn’t grow that fast, but is pretty rapid.
Emerald crabs eat it.

 

[BoralBandit]

+1 for Emeralds, I have two in my tank and they go to town with Bubble algae!

 

[r4rlee]

What is this it Appeared overnight on one rock and the shell of snail

Well i went out today and got 2 Emerald crabs to take care of this thanks for the help