Spa Activator acts as a shock treatment by oxidizing organic matter and containments and lessening the need for maintaining a high sanitizer level. It is also excellent for activating any Chloramines suspended in the water that are often the root cause of unwanted water scent. Highly recommended to be used with all sanitizers; Bromine Tablets, ThermoClear Cartridges and Chlorine. Recommended dosage in a 300 to 400 gallon spa is simply add 2 ounces (for 1 to 2 people and an additional ½ ounce for each additional user) each time after you use the spa and 2 ounces each week when spa is not in use.