This bottle of reagent grade ammonium chloride is for use when fishless cycling. Concentration is 50 mg/L of total ammonia-nitrogen (TAN). Dose 4 drops per gallon of aquarium water.* Use with One and Only Nitrifying Bacteria. 1 drop equals 0.05 ml so this bottle will treat 300 gallons. Generally during a fishless cycle one needs to add ammonium chloride to their tank 3 or 4 times so this bottle is enough ammonia to cycle aquariums up to 250 gallons. Some conversions: 1 teaspoon equals about 5 ml which is 100 drops 1 tablespoon equals almost 15 ml which is 300 drops * NOTE: As of November 1, 2016 we changed the concentration of the ammonium chloride solution so it now takes 4 drops per gallon. The previous version called for 1 drop per gallon. Please see the label on your bottle to determine how much to use. If the bottle say use 1 drop use 1 drop if the bottle says use 4 drops use 4 drops .