Peat
Freshwater aquaria

Peat is sometimes used in freshwater aquaria. It is seen most commonly in soft water or blackwater river systems such as those mimicking the Amazon River basin. In addition to being soft and therefore suitable for demersal (bottom-dwelling) species such as Corydoras catfish, peat is reported to have many other beneficial functions in freshwater aquaria. It softens water by acting as an ion exchanger; it also contains substances that are beneficial for plants and fishes' reproductive health. Peat can prevent algae growth and kill microorganisms. Peat often stains the water yellow or brown due to the leaching of tannins.
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