Lego is a popular toy that many people enjoy playing with, but it can also be dangerous to fish tanks if not handled properly. Lego pieces are small and easily swallowed by fish, which can cause blockages in their digestive systems or even lead to death. Additionally, the chemicals used in some Legos could potentially contaminate tank water and harm your aquatic friends. To ensure the safety of your fish tank when using Legos, it's important to keep them out of reach of curious fish and avoid submerging them directly into the aquarium water. It's also important to make sure any plastic pieces you use are non-toxic so they won't leach harmful chemicals into the water. Finally, always inspect each piece thoroughly before placing it in your tank for any sharp edges that may pose a risk of injury for your beloved pet fish! By following these simple guidelines you can rest assured knowing that everyone will have fun - both you and your finned friends!