So here's a weird one. I've had nerites before and I am
familiar with them occasionally falling onto their backs and sometimes needing a helping hand to get upright.
I got two new nerites to join the couple I already have in my 29G. I am gradually moving my shrimp from a 5 into my new 10 so I split the established filter media between the two and put the two new nerites into the established 5g with a few remaining cherries because it already had lots of algae. Drip acclimated and when I put them in the five they were super active right away. Spent several days absolutely going to town on all the algae. Good, yay.
Fast forward to a few days later, I find them both on their backs. I pull them out to do the smell check and they are obviously still alive, hatch slams closed when I move them and no smell. Ok weird... .well maybe they just fell. So I turn them upright and move on with my day.
Go back later.... they are on their backs again. still alive, still pull back into their shell when I move them.
Every time I put them upright, when I come back they are in the same spot... but on their side again.
temp about 76, no ammonia/nitrites nitrates very low, usually barely noticeable on the color chart. No copper (and if there was I imagine my cherry shrimp would be dying too) kH
~4. There's no fish in the tank to knock them over... what's going on? Any ideas?