Replenish is a proprietary blend of salts designed to replenish physiologically relevant minerals that are removed by reverse osmosis or deionizing filtration. 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. Severe osmotic stress can result in osmotic shock which will lead to rapid death.To restore GH in the planted aquarium, we recommend Equilibrium. meq/L Rating 0-1 Soft 1-2 Moderately Soft 2-3 Slightly Hard 3-4 Moderately Hard 4-6 Hard 6+ Very Hard Directions:Add 5 mL (1 capful) Replenish to 40 L (10 US gallons) to raise GH by 1 meq/L (2.8 dGH). Recommended restoration level into DI or RO water is 1-2 meq/L which is 5 mL per each 20-40 L (5-10 US gallons.)