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What is it?

Dolomite (CaMg(CO3)2) is a natural rock used to add calcium magnesium carbonate to soil to provide calcium, magnesium and carbon to aid plant growth.

It is used in aquariums as a method to increase the general hardness (GH) of the water (and to a degree KH). Many plants, aquatic species require a level of hardness in the water to build their bones and external body parts. For example aquatic snails need a GH of at least 8-10d (142.9-178.6ppm) to stop their outer casing from dissolving into the water and killing the animal.

  • When you add Dolomite to water, it reacts with any acids present and binds with free H+ ions to form Calcium bicarbonate, or Ca(HCO3)2 plus magnesium and thus reduces the count of free H+ ions which raises the pH of the water.


Using supplied in a powder or rock form, it can be added into aquariums where it will slowly dissolve.

Can be used as an alternative source of Lime.