DIATOMACEOUS EARTH - consists of fossilized remains of diatoms, a type of hard-shelled algae. There are a number of varieties, one freshwater diatomite mined in Denmark and often referred to as Danish Pink is used in cat litter which in turn can be used as part of a bonsai growing medium. It is also used as a growing medium in other potted plants.

Bonsai enthusiasts use it as a soil additive, or may even pot a bonsai tree in 100% diatomaceous earth. Like perlite, vermiculite, and expanded clay, it retains water and nutrients, while draining fast and freely, allowing high oxygen circulation within the growing medium.