It sounds like you have a product designed for fishless cycling in aquariums, which is a method used to establish beneficial bacteria in the tank before introducing fish. Using ammonium chloride provides a source of ammonia for these bacteria to thrive on, mimicking the waste produced by fish. Key Points: Concentration: The product contains 40 mg/ml of total ammonia-nitrogen (TAN), which is the form of ammonia that benefits the nitrifying bacteria during cycling. Dosage: The recommended dosage is 4 drops per gallon of aquarium water. This should be done three times throughout the cycling process. Cycling Capacity: 2 oz. (60 ml) bottle: Cycles up to 100 gallons (359 liters). 4 oz. (120 ml) bottle: Cycles up to 200 gallons (757 liters). 8 oz. (480 ml) bottle: Cycles up to 400 gallons (1,514 liters). Recommendations: Its beneficial to download and follow the recipe for successful fishless cycling as it will guide you through the steps and help ensure a healthy environment for your future fish. If you have other questions about fishless cycling, how to use the ammonium chloride, or any other related topics, feel free to ask!