It means that all of the chlorine (Cl) has been removed from whatever the substance may be (typically water)
they need dechlorinated fresh water, and dechlorinated salt water made with aquarium salt.
Very well filtered dechlorinated freshwater. Temperature around 65-72F.
Chlorine is a gas and as such will evaporate off naturally. Boiling the water will speed up the process.
Tadpoles often don't do well in water that is not from the pond where they hatched. It is best to mix dechlorinated tapwater with pond water.
iodine is toxic and present in table salt. Mix salt from the pet store designed for hermit crabs and also offer spring water or dechlorinated water.
Dechlorinated tap water (aka freshwater). Make sure the tank is well filtered and fully cycled, and a suitable huge size for Goldfish, before the fish is bought and introduced!
You can use bottled water but you have to use dechlorinating drops usually carried in the pet isles of walmart or in pet stores
A long twenty gallon fish tank is optimal, but a ten gallon is a good temporary tank. It should be filled up to half way with dechlorinated water and have a rock or other basking spot that it can get out of the water onto.
When you add fresh water to the tank make sure it is dechlorinated, and is the same temperature as the water in the tank. When adding the water into the tank do it slowly so no currents are made in the that could scare the fish or blow them around.
The general rule is that one should change around 25% of the water at a time, thus all you need do is leave your fish in the tank and siphon out 25% of the water, and then replace with dechlorinated water of the same temperature. If you are cleaning a bowl, then it is more common to clean the entire bowl; in that case the fish maybe be placed in a bucket or cup.
Every two days the water should be changed. Otherwise, a filter will have to be installed. Chlorine neutralizing drops (one drop per fish bowl) should be administered to maintain a healthy balance of the water's nutrients and to fully simulate fresh water. Distilled water could also be used which will allow the water to be cleaner for a few days more than dechlorinated tap water.
Your fish can be put straight back in the tank after using dechlorinator, as long as you have not performed a whole water change. A 30% water change every 2 weeks is recommended, and putting your fish back in the tank straight after this change of dechlorinated water shouldn't do them any harm, just as it hasn't done any harm to my 3 healthy barbs (1 rosy, 2 odessas.