Tunze Calcium carbonate 5 liter (1.3 USgal.) bucket.
Calcium carbonate is 99% pure.
CaCO3 (lime) with a grain size of 4 to 6 mm (.15" to .23"). It is ideally suited for use in TUNZE Calcium Automat and other makes of Calcium reactor for buffering the pH value as well as increasing the calcium content.