Fluval Sea Alkalinity: concentrated, alkalinity-boosting compound provides an important energy source for supporting strong coral growthFluval Sea Calcium: concentrated form of calcium is easily absorbed by corals and other invertebrates Two excellent solutions for maintaining optimal pH levels Contains USP (Pharmaceutical) Grade compounds High quality and ultra pure, free of unwanted contaminates Does not contain gluconates, nitrates, or phosphates Helps develop a strong skeletal structure, while not affecting the delicate ionic balance in marine aquariums 2 x 473 mL bottles