Alkalinity, also referred to as carbonate hardness or buffering capacity, is essentially a means of quantifying the stability of pH in a solution, such as aquarium water. Alkalinity is of extreme importance in a marine aquarium, owing to the manner in which it influences pH. In an aquarium, weak acids formed by oxygen respiration and the decomposition of organic material gradually deplete alkalinity. If left unchecked, the alkalinity drops below a critical level and pH begins to fluctuate more wildly than is normally suggested (a daily pH shift of +/-0.2 is normal in marine aquaria), causing stress to livestock. Alkalinity is also depleted by reef-building organisms during the production of aragonite, and is therefore very important for their rapid growth. Maintaining the alkalinity in marine aquaria between 7 - 12 dKH (2.5 - 4.3 meq/L) will generally maintain pH within the desired range. The rate at which alkalinity is depleted in a reef aquarium is determined by the stocking density of reef-building livestock, type of lighting, rate of water circulation, and other biological, physical, and chemical conditions; therefore, each aquarium will have different requirements for the rate of alkalinity supplementation. Once the rate of alkalinity depletion in the aquarium has been determined, the proper dosing rate of this product can be easily calculated. It is recommended that a quality salt mix with the proper (not augmented) alkalinity and concentrations of major, minor, and trace elements be used to establish natural seawater parameters in the reef aquarium, providing a stable ionic foundation on which to build. For additional information on alkalinity and other important aspects of marine chemistry for marine aquaria. All Brightwell Aquatics liquid water care supplements are made with purified water and high purity materials. We develop formulae for aquaria based on empirical data, using observation and measurement rather than theory.