All of my snails came from "thin air". It's possible that they could have come from the ecocomplete, but not very likely. I would guess there were eggs on the plants just sitting and waiting for the right conditions to hatch in. (Then again, I've never known snail eggs not to hatch just because of the environment they are in....don't even know if it's possible for hatching to be delayed... ) .
-Dave
-Dave