We don't have mystery snails in the UK - they are banned! However I have to confess that I an very taken with my Nerites. We had two (Bob and Terry). Bob escaped (or possibly Terry escaped!) and by sheer good luck we found him covered in dog hair several days later. As his little trapdoor was tightly shut we took a risk, crossed our fingers and popped hm back into the tank. After a short time he began to peep out and soon he and Terry (or maybe Bob) were locked in a passionate embrace on a flat rock. I had to cover the dogs' eyes!
Thelma the rams horn appeared with some plants as an egg - some weeks after putting them in the tank this tiny snail was seen zipping about (good turn of speed on her, I can tell you!). She disappeared after a couple of weeks and we assumed she had slithered into the filter and died, but just a couple of days ago she was back, a little larger and just as cute.
Meanwhile we had got another Nerite (Tallulah). Since this one moved in, not only is it like some sort of gastropod orgy in there, but there are eggs appearing all over the place. I know conditions won't allow them to hatch, but they look a bit unsightly, and I'm concerned that if they rot they'll poison the water, so I'm scraping them off when I do the weekly change and hoovering them up. So either Tallulah is a girl and both the lads are besotted with her, or she is a boy and the others are girls and are now in his harem, and everyone has the wrong name.
I read somewhere that is can be good for your snails to have a piece of cuttlefish bone in the tank, for calcium. Is this ok for the fish, does anyone know, and would the amano shrimp benefit from it too.
Asking for an invertebrate . . .