I recently down loaded a free pattern for the cutest pin cushion, a blow fish, adorable. It was stuffed with batting, then they cut a 3 in. circle of fabric, put 7 to 10 penny's in the circle, gathered it up, and tied it off, then placed it in the bottom of the fish. It weighed it down so it could not swim off. LOL I think fish tank gravel would work just as well.The pattern is a free down load at distantpickles.blogspot.com Check it out!!