Boiling water for twenty minutes is a pretty good way of getting rid of all the dissolved gases. Sure, the chlorine will go, so will the oxygen, the CO2 for the plants, the nitrogen, you name it.
Waste of time, money and energy
And you’ll have used quite a bit of electricity boiling the water, which you now need to re-oxygenise by pouring the water into a 5 litre plastic bottle three quarters full and giving it a good shake. Doing that a few times would have gone a long way to kicking the chlorine out anyway without losing the gases in the atmosphere from the water, and saved your electricity bill.
A more excellent way
If you are doing water changes nice and regularly and therefore in any given day are only changing something like 10% of the water, then the level of chlorine won’t upset most aquarium fishes too much. I never bother with it myself and the fish always look happy enough after a change. Warsaw Poland has a bit of chlorine but maybe there are places where there is a lot more chlorination going on, I don’t know. But if the water is safe to drink from the tap then a ten percent change is unlikely to upset most fish so maybe you are just making a rod for your own back…”
Is this the “Talking with imbeciles”, series, or what?
Not really. This is part of a new series where I bring over, updating and re-writing where needed, the best of my answers to questions on Quora. I made a few of these in earlier years in chronological order. For now, I am moving them in the order of the number of upvotes received. These being the ones I would most regret losing. That is what they threatened me with over there for not being a Neo-Marxist. Over the course of 2022, on even numbered dates in the months, I plan to bring home to http://www.huliganov.tv as many of the best of these as I can manage. Where relevant, also to http://www.quoracy.com . I’ll be improving them, updating them, adding images. I warmly invite discussion below in each case. Enjoy!
Original Posting Date: 25/02/2018
Question as answered: If I boil tap water for 20 minutes, would it be sufficiently dechlorinated for my fish tank?
Views at the time added to HTV: 29,100
Upvotes at the time added to HTV: 11
Comments at time added: 0
My Credential for this answer: “I’ve kept fish all my life”