guppy grass care guide

If you’re looking for a beautiful, easy-to-are for, fast-growing plant for your aquarium, guppy grass may well be the very thing you’re looking for.

The plant, also known as Najas grass, is prolific, so you’re never “low” on greenery in the aquarium. It also acts as a filter, algae fighter, hiding place, making it one of the most ideal plants for a freshwater or brackish water aquarium.

Small fish and freshwater eels love it for shelter and others love it for food. It’s a win-win plant.

Quick Overview Facts on Guppy Grass

Scientific NameNajas guadalupensis
Genus: Najas
Other Names: Najas grass, Common water nymph
Lighting Needs: Low to Medium
Growth RateFast
Temperature Requirements: 50 to 86 F
pH Level: 6.0 – 7.0
KH: 2 – 25 dKH
Care Level: Easy
Minimum Tank SizeNano tanks
Maximum Plant Size: 3+ feet

About Guppy Grass

Guppy Grass is an annual plant that (like Anacharis) grows completely submerged in water. It has thin stems which grow long and end in numerous branches. The plant is capable of reaching upwards of three feet in length.

The leaves of this plant are thin, narrow, and flexible. The leaves themselves grow to be around three centimeters long and as wide as two millimeters.

They are green and arranged oppositely on the stem in whorls. The leaves have very small unicellular teeth.

Author Note: Guppy grass is a plant the is part of the Najas genus. It has about forty aquatic plants it is related to and the plants are present in a variety of places.

The plant originated in North America. Today the plant can be found in its home continent along with Central America, the Caribbean, South America, and Asia.

This plant can survive in a wide variety of aquatic habitats. It has been known to inhabit both fast-moving and slower water, still streams, ditches, ponds, freshwater, and brackish water.

There are reports of Guppy Grass also growing in waterways and canals. Due to the wide range of water, this plant can grow in, many countries are starting to consider it an invasive species.

Uses and Benefits of Guppy Grass in an Aquarium

Guppy grass is a hardy plant that offers many great benefits to the aquarium – especially for those with livebearers, egg scatterers, and shrimp.

Providing Shelter for Your Aquatic Life

First off, guppy grass provides your invertebrates and fish with shelter in the aquarium. Whether you’ve got fry looking for a safe one or shy fish looking for someplace to keep to themselves, guppy grass is a winner.

Some critters and fish that particularly appreciate the plant are guppies, celestial pearl danios, catfish of various types, blue velvet shrimp, ember tetras, green fire tetras, platies, rainbowfish, and neon tetras.

Helps Maintain Good Water Quality

Guppy grass works as a good natural filtration addition for your aquarium. It helps to remove ammonia, nitrites, nitrates, and heavy metals.

You’ll still need to do frequent water changes, though, to maintain the overall health of your aquarium.

Makes Good Breeding Grounds

Shrimp, livebearers, and egg scatterers alike love guppy grass for their breeding grounds. Within the plants, the critters can lay eggs and nurture fry safely.

Offering Food Supply

For the herbivores and omnivores in your tank, Najas grass provides some tasty nutrients. Silver dollar, cichlids, goldfish – they all love the plant for dinner and snacking.

Controlling Algae Growth

Because guppy grass is so prolific, it helps to remove excess nutrients from the water that algae needs to grow.

It won’t completely eliminate the possibility of the nuisance growth, but is can dramatically affect the appearance of it.

Boosting Oxygenation

The plant also promotes oxygenation in the tank, which is especially helpful for some species of fish that require highly oxygenated water.

Providing Foraging Spaces

Additionally to providing shelter for new born critters, guppy grass provides some great foraging spaces for fish fry, shrimplets, and other newly hatched aquatic babies.

Raising Aesthetics

Finally, guppy grass is lovely plant. It grows densely, in rich dark green colors and overall improves aesthetics in the aquarium.

Tank Requirements for Guppy Grass

guppy grass with fish

Guppy grass grows in a wide range of areas in its natural environment. From rivers with fast water flow to brackish backwaters, from freshwater clean ponds to stagnant bodies of water – the plant is prolific and flexible.

In the wild, Najas grass typically is in environments of 50 to 86 degrees Fahrenheit, with salinity levels under 8 ppt, pH between 6.0 and 7.0 and dKH from 2 to 25. It’s truly a flexible plant that grow in virtually every kind of water setting save for marine.

Water Parameters

Guppy grass has moderately flexible water condition needs, though it does best in specific ranges.

For temperature, the plant thrives between 72 and 79 degrees, though it can handle temperatures as cool as 68 Fahrenheit.

Top Tip: For pH, guppy grass requires levels between 6.0 and 8.0.

Water hardness is the least concerning water parameter for the plant. It may be anywhere between 2 and 20 GH.

Tank Size

Guppy grass is a rapid grower, but it may be kept in any size fish tank you desire, including nano tanks, community tanks, and more.

But since the plant is a rapid grower, you’ll need to do regular trimmings to keep them from crowding out your fish and other critters in there.

Fertilizer and CO2

Najas grass doesn’t require CO2, soil, or fertilizer. It’s a hardy plant (like Jungle Val) that pretty much takes care of finding its nutrients from the water, waste in the water, et cetera.

However, if you’re growing your guppy grass in a brackish water tank or extremely soft water, you may need to add some fertilizers in that situation. If you do add fertilizers, only use liquid fertilizers.

And though CO2 isn’t needed, there may be cases where injections are useful, depending on the other life in your aquarium. Using liquid carbon doses is the best bet for this plant – and usually others as well.

Lighting Conditions

The plant does best in low to medium light conditions. Ideally, run the lights for 8 to 12 hours daily – no more, no less – for the best health and coloration in the plants.

And though low light is better for helping keep this prolific grower in check, medium light does improve the coloration, making the plant greener and brighter. Under bright lights, the plant actually begins to turn reddish.

Basic Care Guide for Guppy Grass

One unique aspect of guppy grass is that it displays something heterophylly, meaning it changes its leaf shape depending on how it’s grown. If it’s planted in substrate, the leaves vary from how it looks when floating.

The plant itself isn’t a substrate feeding plant, so it actually does best floating, rather than planted (though you may do either, as seen below).

Maintenance for Guppy Grass

guppy grass maintenance

One of the reasons so many fishkeepers love guppy grass is that that it’s extremely low maintenance.

Author Note: It’s actually a highly helpful plant for cutting back algae, which means with it in your tank, you might actually have less overall maintenance for your freshwater fish tank.

The main thing that has to be maintained for your guppy grass is the size and removal of any pieces that break off or melt. Keep it trimmed to prevent overgrowth and light penetration issues, and well, you’re pretty much there.

Common Problems with Guppy Grass

Najas grass doesn’t typically develop a loot of problems in regard to the plant’s health. The issues are more often about the plant causing problems for the fish tank ecosystem.

With that in mind, though, there are a few issues you may need to deal with at some point, if they arise. Primarily, trimming the plant will resolve most of the issues – both for the plant’s health or the health of the fish tank.

Fast Growth/Overgrowth

Guppy grass is a fast grower. This is probably the main problem most folks face with it. It can easily overtake a fish tank if you aren’t careful!

Light Penetration

Because the plant is such a fast grower, it becomes dense and thick rather quickly. This means that it blocks light from penetrating into the tank where other plants, fish, invertebrates, et cetera dwell.

Make sure that you regularly trim the plant and remove cuttings to prevent the plant from overtaking the aquarium and keeping your fish from getting the light they need.


Guppy grass may also melt. This means that the plant has difficulty adapting to the new conditions in the tank. This term refers to leaves falling off aquatic plants.

Typically, this starts with older leaves first. They lose color, then grow transparent, then disintegrate or “melt” away.


Guppy grass has rather fragile stems that break off easily. Thankfully, this is more of a mess-maker than something to be concerned about for the health of the plant.

And, in fact, when the plant breaks, new shoots stem out from the broken pieces and you wind up with more guppy grass plants.

How to Plant Guppy Grass

planting guppy grass

You may plant your guppy grass in one of two ways: via planted root in substrate or as floating plants. Most aquarists prefer letting the guppy grass float, but either is acceptable and works well, so it’s up to you which you choose to do.

If you opt for substrate planting, divide the stems into multiple pieces and root them about 2 inches into the substrate. Aim to space them out properly with at least a few inches between stems.

If the guppy grass you have has been floating already, you’re best off keeping it floating. Converting it from floating to planted may cause melt.

If you decide to float, divide the stems equally and place them around the water column. Easy as that.

If you like doing a mix of both planted and floating, that’s okay, too.

How to Trim Guppy Grass

This plant needs to be trimmed at least once every three weeks, or when you notice that it has started to grow too big for its aquarium.

Due to how rapidly this plant grows, it is important to prevent it from growing so large that it begins to hinder other plants from getting the light necessary to survive and grow healthy.

One method that has helped some people have better control over the plant’s growth is by using medium to high strength lights in tanks that have this plant rooted into the substrate.

The plant will still grow fast, but this may help to reduce the amount of work needed to keep the plant from growing out of control.

The biggest problem that people have with this plant is making sure that it doesn’t grow too fast and starts to choke out all the other plant life around it. Keeping up with the rapid growth and trimming it down are the biggest problems to expect from it.

How to Propagate Guppy Grass

fish swimming wth guppy grass

Guppy Grass is known for growing long along with how it has side shoots that sprout and grow for easy propagation.

These shoots can be snipped off and the clippings will continue to grow by themselves. Even in the wild, when this plant’s brittle stem will easily break and then quickly grow white roots as it floats around.

All that is required for growing additional plants is to break off a few inches from an active and healthy stem. These can be grown as weighted or floating clusters.

Author Note: Another method is to plant the broken-off stem loosely in the tank substrate and it will allow the plant to take root.

This is the kind of plant where propagating isn’t hard, the difficult part is trying to keep the plant from growing out of control. If you start to have too much grown you can always look at selling the extra online or at a local fish store.

In reality, unless you have multiple tanks or a guaranteed way to sell and distribute, making cuts of your Guppy Grass is not a good idea. This plant grows fast and you will end up being overrun with it.

Guppy Grass does produce small staminate and pistillate flowers. However, it does not form fruit or seeds while growing in an aquarium.

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