I'm a newbie too, but I seem to recall a good discussion on this recently. first, I remember someone saying that they can't right themselves if on their backs, so you can turn them over. and secondly, there was a lot of talk about how the nerites seems to go still for long periods of time. the recommendation - do the sniff test. if the smell doesn't knock you over, put 'em back in the tank. 😁 check around for the discussion, it was very good and helpful. good luck.