Sodium thiosulfate is a very safe and effective chlorine treatment (Does not treat chloramines but will threat the chlorine and your biofilter will eat the liberated ammonia, or buy cloramX from www.reedmariculture.com). Below are two stock solutions made up for 1 liter and 1 Quart. To make the stock solutions that treat 50 gallons per mL or 250 gallons per teaspoon simply follow the recipe below. Or you can utilize the fact that Sodium thiosulfate has a solubility of 701 grams per Liter of water. Simply take your container, add hot water as sodium thiosulfate (it's endothermic in water, it gets cold when it dissolves) and add it until it will no longer dissolve. You now have a saturated solution that will treat 1 ppm chlorine in 50 gallons at 1 ml.
