I've had fish get stuck to my filter before. It's an aquaclear 20 in 15 gallon tank. I had a little danio get sucked through multiple times. The funny thing is, he survived (I have no idea how). I eventually took a filter sponge, put a hole in it, made it roundish, and put it over my intake. Everything's been fine since. I have to rinse it out every month or so.
BTW. Beautiful snails!
BTW. Beautiful snails!