Gay's Pondweed

Gay's pondweed is a background plant that behaves like a cross between a vallisneria and a stem plant: it grows tall from a creeping base, produces long narrow leaves, and multiplies through runners and cuttings. It is one of the easiest large background plants for a low-tech tank, which is why it keeps appearing in beginner setups.

Its native range is South American — eastern Bolivia, Brazil, Argentina, Paraguay and Uruguay, a fact that trade listings frequently get wrong by writing 'Africa'. In the aquarium it accepts a wide band of water chemistry, from soft to moderately hard, at a pH of 6 to 8. It does not need CO₂, which makes it a dependable choice for tanks without injection.

Moderate light and temperatures of 18 to 26 °C keep it growing steadily. Propagation is straightforward: runners spread across the substrate and can be cut apart, and stem cuttings root on their own. It grows fast enough to fill a background within a few weeks, so plan to trim. It is only half-hardy outdoors and does not grow emersed, but as a purely aquatic background plant it needs little else.