KORALith is an ultrapure natural calcium carbonate product of the proper grain size for optimum performance in a Kalkreaktor (calcium reactor), which is supplied with CO2 in order to dissolve the media completely forming Calciumbicarbonate. Analysis proves that it is the most phoshate-free product available. The use of KORALith in your reactor will not contribute to hair algae problems. The dissolution of KORALith by your reactor will result in the release of minute levels of strontium, iodine and other important elements to enhance the quality of your water. KORALith is also used in biofilters and as substrate for marine and Malawi/Tanganika aquaria. In all aquaria with alkaline pH values, it creates a natural Calcium - carbonic acid equilibrium. Available in 7 kg (15 lb) plastic reusable tubs. Not a industrial byproduct. Imported from Germany.