I think fish can eat them if they are small enough. They aren't crunchy yet. I've noticed a number of tiny snails in my 6.6 bookshelf. I rarely see any on the side Redfish occupies. Ghost, my sight impaired fella, seems to have most of them on his side. I think Redfish culls the ones he sees, but Ghost just doesn't see them.
They don't seem to bother the fish, the kids think they are cute, so as long as the tank doesn't seethe with them, I'm content to let them live.
The Boy Feesh: Indigo CT, Lavatail CT, Ghost CT, Chicory HM, Redfish VT, Magic DT
The Girl Feesh: Christmas CT, Shine VT, Snowflake CT, Stripes VT, Midnight CT, Grif VT, Tangerine VT, Wraith CT, Amethyst VT, Ice CT, Poe CT, Turquoise II CT