Organic compounds released by botanicals (leaves, wood) that stain water amber and provide antimicrobial benefits - central to blackwater aquariums.
Unit: visible discolorationCode: TANNINS
📖 Overview
Tannins are the reason blackwater rivers look like tea. Leaching from Indian almond leaves, alder cones, driftwood, and other botanicals, they lower pH, soften water, and provide mild antimicrobial protection. Betta breeders swear by Indian almond leaves ("catappa leaves") for stimulating breeding. In an aquarium, tannins are aesthetic and functional - not toxic, but activated carbon removes them if desired.