On two occations, a small garden snail found it's way into my tank of baby snails when I'd clean it & put fresh soil in. I left them there, as it was winter and they would have a better chance of survival. Somehow they escaped in my house and I found them nearly a year later, one on the wall, the other on one of my photograph frames!

I thought it was a mirical they were still alive and as they hadn't eaten for so long, put them back in the tank where they'd get food every day. When I next cleaned it I searched everywhere for them; I had all the other baby snails accounted for, but the 2 garden snails had gone. I've no idea what happened to them; they must have died or escaped again.

Be careful with having garden snails; it's easy to throw them out with old food as they're so small, or equally you can lose them if there's too much soil in the tank.