Elodea najas: fast stems for newly set up tanks

Elodea najas is the narrow-leaved sister of common elodea: the same flexible stems and the same runaway growth, but with fine leaves in whorls that form a far denser thicket. It comes from South America and puts up with almost any water.

Its speed is exactly what makes it useful: it consumes nitrate and phosphate as fast as it grows, so it steadies a newly set up tank before algae move in. The dense thicket also shelters fry and moulting shrimp.

It can be planted in the substrate or left floating, either works. Under medium to high light it grows compact; under low light it stretches and goes bare at the base. Whatever the setup, it needs trimming: reaching the surface it forms a ceiling that leaves everything below in the dark.