Tannins are what typically causes brown or tea-coloured water in ponds. The intensity of the color can range from light amber to dark brown, depending on the concentration of tannins. The most common source of tannins is decaying plant matter like tree leaves, twigs, aquatic plants and algae.

Tannins are what typically causes brown or tea-coloured water in ponds. The intensity of the color can range from light amber to dark brown, depending on the concentration of tannins. The most common source of tannins is decaying plant matter like tree leaves, twigs, aquatic plants and algae.