Guppy grass

Najas guadalupensis

Also known as Najas grass, Common water nymph, Najas, Southern naiad

FreshwaterBrackishStemCuttingsSide shoots

Invasive. Native to the Americas but a vigorous spreader that is invasive in some regions and can quickly fill a tank. Never release into the wild; dispose of in the trash.

Guppy grass (Najas guadalupensis) — no rights reserved · cc0

Care at a glance

Light: Low light
CO2: No CO₂ needed
Growth rate: Fast
Placement: Floating
Type: Stem
Temperature: 64–86°F (18–30°C)
pH: 6.0–8.0
Hardness: 2–20 dGH
Max height: 35.4 in (90 cm)
Spread: 11.8 in (30 cm)
Nutrient uptake: Water column
Growth region: Submersed
Difficulty: Beginner
Origin: North, Central and South America
Family: Hydrocharitaceae

Overview

One of the easiest plants in the hobby and a favorite for fish and shrimp fry, which hide in its dense thickets. Use it floating in the water column for a quick green cloud, or weight it down to anchor in the substrate. It grows under low light with no CO2 and pulls nitrate and ammonia straight from the water, so it doubles as a fast nitrate sponge. The catch is speed: it can grow several feet long, so plan on pruning or pulling 30 to 50 percent of the mass weekly. It is an aggressive spreader and a regulated noxious species in some regions, so dispose of trimmings in the trash, never in waterways.

In the wild

A fast-growing, mostly annual submerged plant found in streams, ditches, lakes, and ponds across the New World, from the United States through Mexico, Central America, the Caribbean, and into South America. It forms loose, brittle, branching tangles of fine toothed leaves and is happy either rooted in substrate or, more commonly, drifting freely through the water column. It tolerates a huge range of temperatures from cool ponds to tropical tanks.

Good to know

Najas guadalupensis sits in the family Hydrocharitaceae and is a true submerged angiosperm, not a floating or surface plant. The genus name Najas comes from the water nymphs (naiads) of Greek mythology, which is where the common name water nymph comes from. The stems are notably fragile and snap easily, and every fragment can root and grow into a new plant.

Did you know

Did you know guppy grass is one of the fastest growers you can buy, and it is so efficient at stripping nutrients that breeders drop a handful into fry tanks both as a living filter and as instant cover for newborn livebearers?