Something is eating my coralline algae!

[fresh]

I don't know what it is, but my coralline algae is being eaten by something in the tank. I do not have any urchins.

I started noticing that it was small random trails just like a snail's trail of disappearing coralline algae on the back wall. Now I notice that some rocks are also missing small patches. The trail is very thin (1 mm or less).

I do have MANY small white snails (less than 1 mm round) which I don't know what they are called. Could they be the culprit? I also have one small chiton (or what looks like a chiton) that is only 0.5 cm long. The chiton I have had for a long time and hasn't grown at all.

What is eating my coralline and how can I stop it? If you can help with your experience, I would greatly appreciate it.

Thanks