The dropsy Colombian finally died. I netted him on Thursday, from the main tank, because he was swimming on his side, and put him in the qt. He died Friday afternoon.
And, giving me quite a turn, I was looking at Ajax on the front glass on Thursday and there is a HOLE in his shell! Argh! Having done a frantic search on the web, it seems that this might be a result of water that is too soft and/or acidic, so we will have to do something about this. Apparently if you correct it in time the snail won’t die, although their shell won’t completely recover. Argh! again.