Guppy grass, Southern waternymph, Najas grass, Common water nymph
Family
Hydrocharitaceae (frogbit family)
Origin
The Americas, from southern Canada through the USA, Mexico, Central America and the Caribbean to South America
Water
freshwater
Maximum size
90 cm
Temperature
15–30°C
pH
6–8
Hardness
3–20 dGH
Care level
beginner
Lighting
Low to medium light; CO2 not needed
Care
Guppy grass is a fast-growing annual of ponds, ditches and streams across the Americas, with slender branching stems 60–90 cm long and thin, slightly see-through leaves up to 3 cm long. Najas (water nymphs or naiads) are slender, brittle, fully submerged plants with narrow, finely toothed leaves, found almost worldwide. Tropica sells it as 'Guppy Grass' and rates it easy. It can float freely or anchor itself with long, fine roots, and suits both aquariums and ponds. Its dense tangle shelters fry and shrimp, takes up excess nutrients and helps oxygenate the water. It is a favourite with beginners. Thin it out regularly so it does not take over. Water figures are our estimate, not from the sources. It is introduced in Japan and Israel. Do not release it into the wild. Sources: Tropica (tropica.com/en/plants); Wikipedia (en.wikipedia.org/wiki/Najasguadalupensis); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.
Breeding
Grows from any broken piece of stem; just pass on a handful. It also sets seed.
Compatibility and tank mates
Perfect for livebearer, fry and shrimp tanks. Goldfish and plant-eating fish will graze it, but it usually outgrows them.
Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.
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