I have been reading here about apple snails and understood that they need a lot of calcium for their shells. Could lack of calcium be the reason for slower development of some of my snails?
Since I have set up a new 80 gal tank I've moved some of my apple snails of the same family there from their old 40 gal home. In a couple of weeks I observed that the snails that remained in the old tank are much smaller than those which were moved. We have hard tap water, so I think that the water in the new tank should contain more calcium.
Also, the mother snail has sadly died recently for no apparent reason in the old smaller tank. She went dormant and slightly active from time to time. I kept on checking her condition until I realized she was gone. Her shell had changed colour a bit before it happened - it became pale. She was probably old - she was quite big when we got her.
But what is happening with her kids? Those which were moved had to undergo some relocation from time to time since I had to treat my new tank for disease with liquid medication and do complete water change twice. However they are still doing fine and look much bigger, more active, and happier than their siblings in the old tank. The temp is slightly higher though in the new tank so that also might affect their active behaviour and growth rate.
Sorry for such a long post - just wanted to give all the info I have.