You have to realise that dechlorinater is an essential to this hobby as much as fish food and water. You really do need a ready supply of it.
Thats a bit of a sweeping statement IMO, The water supplier puts enough chlorine in the water to kill small bacterial colonies, our bacterial colonies are at least a million times bigger than this so not using dechlorinator on a small 20% water change isn't going to do much. With regards to the fish, the chlorine will have gassed off within a few hours, so it isn't long enough to harm the fish. I know of discus keepers that do 80% water changes with no dechlorinators, I haven't used dechlor for at least 6 months, and I do 50% per week.
There was a debate in the scientific section a few years ago, and we quickly came to the conclusion the dechlorinator is not essential.
Chloramine will have its bond to ammonia broken down by our bacteria and the ammonia will be processed leaving the chlorine to gas off incase anyone was wondering why I missed it out.