Depending on how “dirty” your tank is. They like to clean the glass and rocks of algae. It’s possible if you feed some additional nori in the sump for them to eat. What would be the purpose of keeping these snails in a non-lighted sump if I may ask?
I decided against that. These are Ora trochius, for some reason the majority can’t turn themselves back over. They aren’t old, received as very young from AGB. The red banded trochius I’ve had in the past don’t have this problem. I’ve sourced the red banded and they are incoming.