Awe... I'm sorry to hear about your snail. image Crawl free little fella...

Unfortunately, it's hard to "think like a snail" and have every forethought as to the trouble they can get in. I covered all of the openings so they cannot get out of the tanks... but I once found one of my nerites in the filter... image Thankfully, it didn't seem to go through the impeller mechanism, or I'm sure it would have been a terrible sight. image So now I put plastic canvas over or behind my filter openings to ensure they cannot get in there too. They are pretty wiley... and curious... image

Michele