To protect the human population from dying off from drinking contaminated water, local water companies add chemicals such as chlorine and chloramines to disinfect the water from harmful organisms that can make people sick. This treated tap water is perfectly safe for humans but can be extremely deadly to your aquarium fish. Conditions Tap Water helps condition aquarium water by neutralizing harmful chlorine found in tap water. This product also has properties to precipitate and detoxify heavy metals so that these elements do not affect the aquarium's fish or plants.