What is this green thing on my snail?

[Gyurooo]

Hi,
I tried to search and google but did not find any answer. I just noticed this green thing on my snail's shell. I tought its bubble algae but its string like almost like a small worm but solid not moving and forms an "arch". Also what are those red strings? Should I take out the snail and brush it off or is it harmless?

Thanks

 

[badger89]

Look like algle I brush mine when is gets bad