ReefPure Kalkwasser is the premier Calcium Hydroxide product available today. It is produced entirely from ultra-pure Calcium Hydroxide, the highest quality raw material in the hobby. Inferior competing products are produced using poor quality Calcium Hydroxide, this inferior Calcium Hydroxide contains up to 30X the heavy metal concentration, including Lead compared to ReefPure Calcium Hydroxide. Warner Marine Research is the only manufacturer to use these fine quality raw materials. Most importantly ReefPure Kalkwasser is highly effective at adding high quality bio-available Calcium without the unnecessary impurities found in the competitors products.