The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
They're food-grade escargot shells, so you know they are fish-safe. They're light enough for the fish to move around in the tank (unlike the green turbos I used to supply my shellies with). Plus, my wife says they're "kind of pretty" so they won't ugly up your tank.