Fish need clean, chemically balanced water to thrive. Any time tap water is added to the aquarium, a water conditioner must be used to remove any chlorine/chloramine that is present.
Image from Petsmart
Can fish survive in chlorinated water?
Chlorine toxicity commonly occurs when a novice fish owner, unaware of the dangers of chemically treated faucet water, fills the tank with chlorinated tap water rather than taking the time to properly aerate and treat the water. Chlorine poisoning is often fatal to fish if it is not caught, diagnosed and treated quickly.
Chlorine kills living cells, most often damaging fish's sensitive gills as well as the skin that covers their entire bodies. Fish placed in chlorinated water will begin to suffer from respiratory problems and may suffocate, unable to breathe properly.
Preventing Chlorine Poisoning
Never use tap water in your fish tank without first treating the water with chemicals that neutralize the chlorine in the water, or by boiling it or aerating it with plenty of oxygen. If you use a chlorine-based product such as bleach to clean and disinfect anything you use in your fish tank, you need to make sure you thoroughly rinse those objects in clean water to prevent introducing chlorine into your tank. Image from PetsonMom
Also, make sure to buy aquarium test strips that allow you to test your tank for chlorine. Regular chlorine testing will help you identify problems in your tank. If your tank has too much chlorine in it, you will need to completely empty the tank and perform a full cleaning on it before you refill it with properly treated water. Be sure to rinse all tank accessories and equipment thoroughly before returning them to the tank.
If you are in any doubt as to how you should care for your fish, particulary as it pertains to the water you use, please consult a trusted pet store for details.
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