- This secret stone is a beautiful cave where fish can breed, play and rest. Beta, shrimp, guppy, snails… Will love it. 2. Suitable for small fish, easy to clean, conducive to breeding nitrifying bacteria and improving water quality. 3. Granite ceramic material, non-toxic to fish. No color, no smell. 4. No sharp or rough edge, no fender scratching problem. 5. A beautiful coral reef that creates a natural and vibrant environment for your aquarium. Size: 106.55cm