Seachem replenish is a proprietary blend of salts designed to replenish physiologically relevant minerals that are removed by reverse osmosis or deionising filtrationr replenish restores general hardness gh using a balanced blend of both soft sodium potassium and hard calcium magnesium salts restoration of mineral content is essential since a complete lack of minerals will result in osmotic stress in those species whose osmoregulation systems are adapted to a mineralized environment