Aquarium Plants

Najas Guadalupensis (Guppy Grass) – Care Guide

Would you like to grow plants in your freshwater aquarium, but don’t because you’re worried you don’t have the right equipment? Then you’ll probably love the fast-growing aquatic plant known as Guppy Grass: Najas Guadalupensis. These aquarium plants are easy to grow and do not require any special equipment to thrive in your tank.

Introduction to Najas Guadalupensis (Guppy Grass)

One downside to having a planted freshwater tank is the expensive lights and special fertilizers needed to keep many aquatic plants from turning brown and dying in your aquarium. If you are looking for one of the easiest low maintenance aquatic plants, consider growing Common Water Nymph aka Guppy Grass or Najas Grass !

What is Najas Guadalupensis (Guppy Grass)?

Guppy Grass (Najas guadalupensis) is an annual aquatic plant commonly found in streams, ditches, and ponds throughout the New World. It is grown as a floating, weighted or rooted aquarium plant and is ideal for shrimp and fry tanks. It also removes toxins and helps oxygenate the water.

While these plants are native to North, Central and South America, Guppy Grass has been introduced into waterways around the world and may be considered an invasive species in some places due to its uncontrollable spread.

Appearance and growth habits

Guppy Grass is a popular choice among aquarists of all experience levels due to its fine leaf texture and fast, uncomplicated growth and propagation:

  • Guppy Grasses have thin, almost transparent green leaves about 3 centimeters long and 1 to 2 centimeters wide, which grow on opposite sides of the stem in a spiral pattern and are edged with tiny single-celled teeth.
  • They have multiple slender, branching stems that are very flexible and can reach up to 3 feet in length if not clipped back.
  • This plant can be grown as a floating plant, but can also be rooted in its substrate or held in place using plant weights.
  • They are easily propagated from stem cuttings and do not require intense lighting conditions or CO2 injection to thrive, although using a basic liquid fertilizer can be helpful in some situations.

Care Tips: How To Use Najas Grass In Your Aquarium

Najas is an ideal choice for any planted or aquatic habitat, but is especially preferred for breeding facilities and shrimp tanks. It was originally a favorite of guppy breeders, hence the nickname «guppy grass,» but its fast growth, easy spread, and fine texture also make it a desirable background plant for community tanks.

Najas uses include:

  • Plant or float a bunch to provide a thick growth of fine leaves and stems that protects and shelters delicate fry and invertebrates, and helps trap microscopic food particles. to feed them.
  • Grow these plants as a cool snack for your vegetarian and omnivorous fish such as goldfish, some freshwater sharks, and algae-eating fish.
  • These herbs quickly absorb excess nutrients in your tank’s water column and help keep the water clean and prevent nasty algal blooms.
    • Guppy Grass specifically remove toxins like ammonia, nitrate and nitrite, but they also absorb heavy metals and almost every other nutrient in the water!
    • They are often used in heavily stocked tanks to reduce the load on filters, in addition to their anti-algae properties.
  • Fast growing aquatic plants like Guppy Grass will also produce a lot of oxygen and help prevent Dead Zones from developing in your tank.
  • You can use Najas Guadalupensis as a background plant loosely rooted in the substrate or supported with plant weights or floating bundles in your water column.
Benefits of Growing Najas Disadvantages of using Najas
Provides shelter for small fish, shrimp and fry. Regular water changes are needed for healthy growth and propagation.
Filters toxins and waste products You may need to use a weekly liquid fertilizer
Absorbs nutrients to prevent algal blooms Frequent pruning and removal is usually required to control growth.
Produces oxygen and prevents dead zones.
It is a fast growing floating, rooted or ponderous plant.

How to take care of grass guppy

Guppy Grass is not a picky plant and generally thrives in most aquariums without much effort. Honestly, it is often more difficult to control its growth and spread than to stimulate it ! Let’s take a look at some tips for growing this plant in your aquarium:

Tank configuration, water parameters and lighting requirements

Guppy grass can be kept in aquariums of all sizes, but its fast growing habits mean it can quickly overwhelm smaller Nano Tanks if not pruned frequently. It can also cause problems by clogging your filter intakes, and performs best in tanks with minimal flow and current. These grasses:

  • They thrive on 8 to 12 hours a day of low to moderate lighting conditions, so you may not even need an additional light fixture for your setup if your tank is in a bright spot.
  • Prefer water temperatures of 68 to 79°F and do well over a wide pH range of 6.0 to 8.0.
  • They are not particularly sensitive to water hardness and tolerate 2 to 20 degrees of general hardness (dGH).

Fertilization, substrate and maintenance

Guppy Grass draws nutrition directly from its water column, so there is no need to use an enriched plant medium or fertilizer tablets and it can grow in any type of soil, sand or gravel. You can even go for a bare bottom tank and simply float your grass on the water if you prefer. Najas Guadalupensis are very easy to maintain:

  • Like all aquatic plants, regular water changes are key if you want a thriving lawn garden and also help replace the essential trace minerals and nutrients that they absorb from your tank water.
  • These herbs use the ammonia and other organic waste in your tank for food and help keep the water clean and well-oxygenated.
  • If your lawn isn’t growing very fast or is looking a little yellow from lack of carbon, you can use a balanced liquid fertilizer once a week to give it a boost, but there’s no need to invest in CO2 diffusers or injection systems.

Common problems

Najas Guadalupensis present a common problem to aquarists: they grow so fast they can quickly take over your entire aquarium! If you don’t regularly and frequently prune vegetation and remove excess growth from your tank, they will spread out and block all light from reaching your other plants and animals.

These plants sometimes suffer from a condition called “ Najas Guadalupensis Meltdown ”. When your growing conditions suddenly change. Right after planting stems in your substrate, the leaves may look droopy and almost as if they are melting. Herbs may take a few weeks to recover and produce fresh, normal-looking leaves.

life cycle and propagation

Guppy Grass is an annual aquatic plant that is propagated through cuttings. Its brittle stems break easily and a fractured stem will quickly form small white roots. while floating in the water. While these herbs produce small, inconspicuous staminate and pistillate flowers, they do not form seeds or fruits in an aquarium.

To propagate your Guppy Grass, all you have to do is break off a few inches of an actively growing stem! You can grow these grasses as a floating or heavy bunch, or you can plant the stems loosely in your substrate and allow them to take root. To plant your grasses in substrate:

  1. Collect or purchase a bunch of fresh stem cuttings 4 to 6 inches long.
  2. Using your finger or planting tools, gently push the bottom of each stem about 1 inch into your substrate, or deep enough to prevent the stem from floating.
  3. You can plant the stems close together to form a dense clump of growth or spread them farther apart for a looser, grassy forest appearance.
  4. Do not plant stems deeply, as roots will develop near the surface.
  5. Occasionally replant fresh stem segments to replenish your grasses.


Najas Guadalupensis are a popular choice for a wide range of community planted aquariums and are suitable for almost all freshwater setups. Whether you keep semi-aggressive Barbs or Cichlids or have a Peaceful Rainbow Fish or Tank Gourami, the purifying powers of these grasses will benefit your community.

Live fish breeders such as Guppies, Mollies, Platys and Swordtails use clusters of Guppy Grass to raise and protect their fry. But they also provide protection and food to communities with:

  • Small nano fish like Tetras, Rasboras and Minnows.
  • Freshwater invertebrates like Cherry, Ghost and Glass Shrimp and Nerite, Malaysian Trumpet, Mystery and Assassin Snails.
  • Omnivorous catfish such as the Otocincluis, Siamese Kelp Eater, and Bristlenose Plecostomus.

Guppy grass, Common water nymph, Najas grass

up to 3 feet if not trimmed back

Ideal for breeding, shrimp and community tanks, and especially for housing small animals and fry. They are also a good choice for heavily stocked tanks as they remove toxins from the water.

Floating, planted in substrate or secured with plant weights

Vertical growth cuttings and lateral stems.


Even if you are not keeping guppies, having Guppy Grass or najas in your aquarium offers many benefits. These fast-growing, low-maintenance plants remove toxins from your tank and provide shelter and food for small fish, shrimp, and fry. We’d love to hear about your experiences with these plants, so please leave a comment below or join our community on social media.

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