Check the listing for details. RA API Aqua Essential - 8 oz. Condition: New. Listed at 20.65 USD. API Aqua Essential is a professional grade all-in-one water conditioner designed for use in freshwater, saltwater and planted aquariums. Even in small amounts, ammonia can be harmful to fish and is regularly released through biological waste and leftover food, but Aqua Essential quickly removes toxic ammonia, nitrite and nitrates from the aquarium.