Concentrated Liquid Calcium provides bio-available calcium for lush growth of purple, pink and green calcareous algae, snails, hard tube worms and clams. With regular use, corals will open more and stay attached to their skeletons better, . Phosphate & nitrate freeContains no gluconates, EDTA, or other organics to raise DOC levels, as many competing products doConcentrated Liquid Calcium alone can provide all the calcium your reef will need, but for maximum results, use Kent Marine Kalkwasser Mix first, then raise calcium level with this product.