Repti Calcium With Vitamin D3 is a phosphorusfree calcium supplement for reptiles and amphibians. We use only Precipitated Calcium Carbonate which is white in color and is essentially lead free. Impurities in other sources of calcium carbonate (e.g. Oyster Shell Calcium) cause the supplement to appear grey. With Repti Calcium, you can take comfort in knowing that your reptiles are getting a highly bioavailable source of calcium carbonate that is free of harmful impurities. Zoo Med Repti Calcium 85gm. A34-3.