Each bag contains unwashed Lava Stone in Medium, 0-10mm particle size.
Crushed lava stone or its Japanese name, Fujizuna is an attractive and entirely natural product being a volcanic byproduct, for use in aquariums, terrariums, and forms an important component in bonsai tree and succulent mixes when combined with akadama and pumice.
Lava rock or scoria as volcanic rock is also referred to, adds spacing or passageways through which air can flow and prevents compaction of growing mediums. It has a potentially long lifespan as it does not break down and can thus be reused. Due to its high porosity it allows water and fertilizer penetration and storage.
The most popular mix containing lava would be 1 part small lava:1 part small akadama:1 part small pumice. To increase water retention use more akadama (eg when potting deciduous trees) This is affectionately known as the 'Boon mix' after its author bonsai professional Boon Manakitivipart.
Lava stone is very effective at creating the ideal living environment for your aquarium as due to its porosity it provides plenty of surface area for beneficial denitrifying bacteria to develop. This beneficial bacteria has the ability to improve water quality by removing nitrates. Shrimp will also forage on Lava stone as small particles of food may become lodged in the millions of open cavities. Lava stone is also extremely popular with cichlid enthusiasts in their tank setups.
Lava stone has an SG greater than 1.0. It does not float in water.
Much of the advantages of using crushed lava stone in a growing mix has been covered in the bonsai section and I dare say that the same 'Boon mix' would be ideal for many succulents. Essentially the lava stone provides structure to the medium as it does not degrade and is a very porous particle which retains moisture but permits free flow of air.