So my partner found this weird little guy in the tank where he keeps his sun beetles, and we're trying to figure out what it is.
It's about 6mm across the shell and we live in the UK, if this is helpful.
Our only guess is it might be a Discus rotundatus, but they have more whorls to their shells. It could be a non-native species I guess- we kept it just in case- but we can't think where it would have come from in that case.
thanks a lot for informations about the width of the shell and the location (that's always extremely helpful).
I'm pretty sure it's family Hygromiidae, genus Candidula. Perhaps Candidula intersecta, which is pretty common in UK. I suppose it to be juvenile (C. intersecta reaches a width of 7 to 13 mm at the best).