BioGuard Balance Pak 300 is a calcium hardness increaser. This product boosts calcium hardness to help prevent equipment corrosion, etching of plaster and wrinkling of liners. It has a unique palletized formulation which means faster dissolving and less cloudiness. Low calcium hardness can cause staining, etching, or distorting of the pool's finish. Plaster etched by low calcium hardness will become abrasive and uncomfortable for swimmers. Rough plaster also increases algae problems and makes cleaning more difficult. It is important to keep your pool water balanced in order to get the most effective use out of your chemicals.