TankBud

Guppy grass

Najas guadalupensis

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

FreshwaterBrackishStemFragmentationCuttings

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)
Aquarium Plants Factory · Used with permission

Care at a glance

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

Overview

Guppy grass is a beginner plant and one of the easiest in the hobby. It is also one of the fastest growers you can buy, forming dense green thickets.

Did you know

Guppy grass strips nutrients so efficiently that breeders drop a handful into fry tanks as a living filter. The same tangle gives newborn livebearers and shrimp fry instant cover.

Caring for guppy grass

Use guppy grass floating in the water column as a quick green cloud, or weight it down to anchor it in the substrate. It grows in freshwater and in brackish tanks.

It grows under low light with no CO2. It pulls nitrate and ammonia straight from the water, so it doubles as a fast nitrate sponge. Keep it at 64 to 86°F (18 to 30°C).

Speed is the catch, since it can grow to about 35 in (90 cm) long. Plan on pruning or pulling 30 to 50 percent of the mass every week. The stems are fragile and snap easily, and every fragment can root and grow into a new plant.

Guppy grass is an aggressive spreader and a regulated noxious species in some regions. Dispose of trimmings in the trash, never in waterways.

Good to know

Guppy grass, Najas guadalupensis, sits in the family Hydrocharitaceae and is a true submerged angiosperm. The genus name Najas comes from the water nymphs, or naiads, of Greek mythology, the source of the common name water nymph. Its stems branch into loose, brittle tangles of fine toothed leaves.

In the wild

Guppy grass is a fast-growing, mostly annual submerged plant of the New World. It lives in streams, ditches, lakes and ponds from the United States through Mexico, Central America and the Caribbean into South America. It grows rooted in the substrate or, more often, drifting freely through the water column. It tolerates a huge range of temperatures, from cool ponds to tropical tanks.

Common questions

Does guppy grass need to be planted in the substrate?

No. Guppy grass can drift at the surface or be anchored in the substrate. It takes its nutrients from the water either way.

Does guppy grass need CO2?

No. Guppy grass grows well without added CO2 and suits a low-tech tank.

How much light does guppy grass need?

Guppy grass is a low-light plant, and the light that comes with a standard tank kit is enough for it.

How do you propagate guppy grass?

Guppy grass propagates by fragmentation and cuttings. Pieces that break off keep growing, so pulling a clump apart spreads it. Any length of stem cut off grows into a new plant.

How tall does guppy grass grow?

Guppy grass grows to about 35.4 in (90 cm) tall. It grows fast, so expect to trim or thin it out often.

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