You DO NOT want it
in YOUR pond !
CHLORINE BURNS FISH !
IT CAN SEVERELY DAMAGE THEIR SKIN, SCALES & GILLS AND , IN SEVERE CICUMSTANCES, IT WILL KILL THEM.
Chlorine is added to drinking water in most parts of the world to kill bacteria. It therefore follows that if you fill or top up your pond from the tap, you are adding chlorine to it and putting your fish at risk.
The equipment used to remove chlorine from water is called a dechlorinator. In simple terms a dechlorinator works by passing water through activated carbon and out into the pond providing chemically cleaner, chlorine free water.
The chlorine content in water varies from area to area and so there are no hard and fast rules as to how long the carbon will work before it is exhausted and needs to be changed, However, the life of the carbon can be prolonged by regularly back-flushing the unit (this should also be carried out before use the first time).