Use 10 drops per gallon, or 1 teaspoon (approximately 5 ml) per 10 gallons of water, or 4 ounces for 240 gallons of water. This standard dosage produces a concentration of 15 ppm (= 15 mgL) formalin and 0.05 ppm of malachite green. NovAqua+® and AmQuel+® are recommended.