For my 3 largest tanks, 60, 30 and 20 gallons, I use a python connected to a sink to remove and add water. My well water does not contain chlorine but it has a nitrate level of 30 ppm. I plumbed a nitrate binding filter to the cold water faucet. I add just enough hot water, which contains nitrate, to the cold water bringing the water temperature to 77F. So I’m adding water with a nitrate level of about 5-10 ppm.