It has spiral, stalked leaves that are papery to thinly leathery, dark green above, yellowish green below, and will turn red before falling. Each leaf is reverse-egg-shaped, 8–38 cm long by 5–19 cm wide, with 6–12 pairs of veins arising from the main vein of the leaf, and a pair of glands at the base of the leaf. Keeping the leaves in an aquarium may lower the pH and heavy-metal content of the water. It has been used in this way by fish breeders for many years, and is active against some parasites and bacterial pathogens. It is also believed to help prevent fungus forming on the eggs of the fish. While common in hobby fishkeeping, this use of catappa leaves is not used in commercial aquaculture.
