Because municipal water is treated with chemicals, and because the city of St. Paul artificially elevates the pH to protect all the lead pipes from corrosion, I age my tap water and add a product that removes the chloramines (a chlorine/ammonia combination) that would quickly kill the fish. A few days of sitting in a barrel also drops the pH a bit. Two large trash cans and a 50 gallon barrel hold almost enough water for changing all of the tanks. One of the barrels is left "as is", while the other two get Epsom salts, baking soda and marine salt to create the "harder" preferred by many cichlids, and most livebearers. Two 5 gallon buckets have much harder water for the Tanganyika cichlids, and a dilute sea water mixture for the brackish water fish (the mudskipper, and Edd my puffer). Yep it's lot of work!
Two of the water barrels have heaters in them as many of my fish are tropical and one barrel is left at room temperature for the fish that do best at room temperature. I have a trusty pump with a hose attached for pumping water back into the tanks. If I had the money to do it, I'd have all my tanks plumbed and be able to do water changes with the flip of a switch - but not in this life!