A lot of municipalities switched to chloramine instead of chlorine because it doesn't gas off and they can get away with using less of it...if you're on public water they can tell you which form they use, good to know if you plan on using the 'gas it off' method in the future. At the risk of sounding like a product endorsement, this stuff called Prime has really saved my butt when it comes to making taking care of my fish easier. It neutralizes chlorine, chloramine, and heavy metals, and it converts ammonia, nitrite, and nitrates to forms that are less harmful on fish but still available for the bacteria to work on (helpful if there's a spike but no immediate time to do a big water change). There are a lot of products on the market that do the same thing, but I prefer Prime because it's all in one bottle and it's pretty concentrated so I don't have to use much. My water changes are a lot easier...stir up the substrate, use a hose to drain into my flower beds, add some Prime to the remaining water, attach the hose to my faucet, match the temp, and let er rip to fill it back up. Prime's supposed to start working as soon as it hits the water, but with super sensitive fish like discus I'd still pre-mix it just to be sure everything's completely neutralized before it gets to the fish.