Using tap water in your aquarium can be a convenient choice, but straight from the tap, it is unsafe for fish. Water suppliers add chlorine and chloramine to tap water to kill bacteria, which is harmless to humans but toxic to aquatic life. Before adding tap water to your tank, you need to treat it properly. Tap water contains a variety of harmful substances such as chlorine, chloramine, and heavy metals. To make tap water safe for your aquarium, you need to use a water conditioner or dechlorinator. These products neutralize chlorine and chloramine, along with removing heavy metals from the water, ensuring that it’s safe for your fish. When replacing the evaporated water, always treat it with a dechlorinator. This ensures that the new water added doesn’t harm your fish.