Chlorine & Chloramine are both chemicals used in our drinking water to help kill off germs and make it safer for us to drink.
Fish, on the other hand, don’t like these chemicals and if the concentration is high enough it will kill them. Lower concentrations of the chemical may not kill the fish, but will cause long term damage to the fins and gills.
Chlorine is a gas that is put into the water under pressure. When the water is exposed to free air the gas will escape back into the atmosphere over time.
This takes a few days, and I would recommend a dechlorinator (water conditioner) be used to speed up the process, as well as a test kit to make sure that all the Chlorine is out the water before you put any live stock in your fish tank.
What you need to do is set up your fish tank how you intend it to be, with gravel, decorations, pumps and filters. Then fill it up with water and switch it on. It can take up to 5 days to get the water right, but it will depend on the quality of the water you put in and any additional treatments you may have used.
Running your aquarium like this also serves as a test for your equipment. You make sure all your pumps and filters are operating like they should, as well as checking the entire system for leaks.
Remember that the test kit will be used at all stages of owning an aquarium, not just the initial setup stage.
The down side for us trying to start an aquarium is that it is harder to get rid of. It doesn’t escape from the water as easily as Chlorine does.
I would also recommend a dechlorinator be used to remove this chemical the same as with Chlorine. Most water conditioners will be effective against both, but some may have additives to counteract the Ammonia that is left behind when the chemical is broken down. Check the manufacturer’s instructions. A healthy bio filter should be able to counteract the trace Ammonia that is left behind, if you are only doing a small partial water change.
In summary you need to remember that these chemicals, as well as Ammonia, are all harmful to fish. Do the necessary tests to find out if there are any traces of them in the water, and take steps to remove them.