Two Little Fishies Calcium Concentrate 500 ml. 16.8 fluid ozCalcium ConcentrateJulian Sprungs Reef FormulaTwo Little Fishies Calcium Concentrate makes it easy to rapidly adjust the calcium level in an aquarium. The long term maintenance of calcium levels is best managed with a balanced ion supplement such as Kalkwasser or Two Little Fishies C Balance, which maintain alkalinity in addition to calcium concentration. Use Two Little Fishies Calcium Concentrate to raise the calcium concentration when the alkalinity level is already high.In this case, Calcium Concentrate will simultaneously raise the calcium concentration and lower the alkalinity level, bringing both closer to a natural seawater ratio. When the calcium and alkalinity levels are properly balanced, stop using Calcium Concentrate, and continue using a balanced supplement such as C Balance, which provides carbonates and bicarbonates, calcium, magnesium and strontium in the correct ratios.