Sand, on the other hand, does get stuck in frogs' digestive systems, as revealed when I took my frog to the vet and got an X-ray because she had a lump in her belly. I removed sand from the tank as soon as the vet said it was a problem (in May 2003); as of December 2004, sand still occasionally appears in the aquarium. The stuff can get really stuck in a frog, which is a problem if it piles up.