Grapefruit Seed Extract (GSE) is a substance derived from the seeds, membranes, and the pulp of grapefruit. Used as a broad-spectrum, non-toxic, antimicrobial product, it is known to be highly effective for fighting infection and promoting health. GSE is used as a purifier, antiseptic, and preservative. Even in studies comparing its effectiveness to chlorine bleach, isopropyl alcohol, and colloidal silver, GSE has been found to be superior as an antimicrobial. To use in fresh water. Add one (1) drop per 16 oz. of fresh water, shake well, wait 10 minutes and it's ready to clam your thirst!