Little clear flat snails?

[chris]

little clear round but cup shaped snails? anyone know if these hurt an axie or are they ok. I feed alot of night crawlers could they come from them? if they are bad how can i get rid of them they came from nowhere

 

[joan]

Limpets. Natural tank fauna. Annoying, but harmless. You can scrape them off with a hard plastic card (credit card) or your fingernail.