Strange Semi Circle things not moving in tank

[Jess89264]

I have a tank on a fishless cycle, it’s brackish and has an Anubis plant in it - some snails have hitchhiked (common ones I think?)

nd I’m unsure if these white semi circles are their poo?! I wouldn’t think it would be white though.
They don’t move, are all over the plants and wood?!
Picture attached

 

[reef lover]

Yup snail poo...