My snails ignore it or kind of slide right over it. Even if they did nom some, it's usually just the dead stuff. To care for it, just rinse it off and squeeze it gently about once a week. They act as a sort of natural filter and can get a it clogged if sitting in a tank, especially an unfiltered one. Mine doesn't get much light and is still doing great so I think low to medium light is ok for them, even though they'd probably thrive with some more light.