Anti Chlorine and neutralize Chloramine. Cost-effective than those anti-chlorine bottles in aquarium shops. Hypo crystal (Sodium thiosulfate) Application: Fish tank dosage: 10 liters of water plus one gram (one gram of 2-3 capsules) Pond dosage: use 10 grams of this product in one cubic meter (about 2-3 capsules per gram) Use once a week, or add one time each time you change the new water to remove the residual chlorine and excess ammonia nitrogen, and wait until it is completely dissolved in the new water before you can pour it directly into the fish tank. Fishponds can be directly spread evenly.