How much tap safe to use in a 2ft fish tank?

Using tap water in a 2ft fish tank can be safe, but it depends on the water quality and the specific needs of the fish. It's essential to treat tap water with a dechlorinator to remove harmful chlorine and chloramines. Additionally, testing for pH, ammonia, nitrite, and nitrate levels is crucial to ensure the water parameters are suitable for the fish species you plan to keep. Regular monitoring and water changes will help maintain a healthy environment.