A compressed accumulation of partially-decomposed, chiefly vegetable matter typically found in certain marshes, bogs, and peat swamp forests throughout the world. It forms via breakdown of various plants and other organic materials in water when full decomposition is prevented due to localised acidic, anaerobic conditions. As a result of this somewhat specific nature the organisms inhabiting peaty environments are often stenotypic and found nowhere else. Peat can be used as a fuel when dried and thus has industrial importance in some countries. Also used in aquaria, especially in order to simulate blackwater habitats, either in pure, artificially-granulated or liquid extract form.