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Guppy Grass Care, Information, & Pictures

If you’re looking for a bulletproof plant, your choices are typically Java Fern and Java Moss. Most plants, especially stem plants, tend to be more delicate and demanding.

They want nice, strong lighting, extra carbon dioxide, and a rich substrate full of nutrients. And if they don’t get that they will wither and fade.

However there is one stem plant that’s much more durable. In fact, it thrives in the same dimly lit conditions that Java Fern and other hardy plants do. I’m talking about Guppy Grass, an aquarium staple that’s well worth getting to know!

What is Guppy Grass?

Guppy Grass is an aquarium plant most of us have heard of but not everyone has grown. It’s inexpensive and rather untidy and ordinary in appearance. Most of the time aquarists prefer saving their dollars for fancier-looking plants like Ludwigia or Sword Plants.

But the humble Guppy Grass is a plant that’s been in the hobby way longer than any of these fancy newcomers. As a North American native it’s been used for aquascaping for as long as there have been aquariums, container ponds, and earthen ponds to stock!

Guppy Grass can be found from Canada down to Mexico and into South America and the islands of the West Indies. Unfortunately, it’s cosmopolitan nature and rapid growth makes it the perfect invasive species. Najas guadalupensis has also become naturalized in Japan, Israel, and Palestine, where it outcompetes native organisms for light and real estate.

However in the aquarium, it’s hard to beat for sheer ease of care. It can be grown in low light tanks, floating, or rooted. It produces greenery quickly and provides shelter for animals and fry. The thickness of its growth helps baby Guppies survive to adulthood as they would otherwise be eaten by their parents, hence the name ‘Guppy Grass.’

What else is there to know about this hardy, easy to care for plant?

  • Common Names: Guppy Grass, Najas Grass, Southern Water Nymph, Common Water Nymph
  • Scientific Name: Najas guadalupensis
  • Origin: North & South America (invasive in Japan, Israel, and Palestine)
  • Height: Up to 1 meter
  • Light Needs: Low
  • Growth Rate: Fast
  • Ease of Care: Very Easy

Guppy Grass Care

The section contains Guppy grass care topics such lighting, water parameters, propagation, and more.

Lighting Requirements

Many common aquarium plants won’t do well under the stock lights that come with your average tank. These lights may look bright but they almost never provide photosynthetically active radiation (PAR). PAR is the specific wavelengths that activate photosynthesis in plants and help them produce sugars for food.

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You can get PAR by using aquatic plant LED lighting, which is far more affordable than it used to be. That said, as a low-light plant, Guppy Grass will grow fairly well without it. But it grows like an absolute weed with the right spectrum!

With PAR lighting you’ll see denser, more compact growth rather than a sprawling weedy habit. As it grows close to the surface you may even see red pigmentation begin to form in the stem and higher leaves, a sign it’s loving the intense light.

If you know your lighting is on the weaker side, you can allow your Guppy Grass to float instead. By staying near the surface it will be able to get all of the light it needs even from weaker incandescent or fluorescent fixtures.

Planting & Propagation

Guppy Grass is incredibly versatile. You can plant it in any style – few plants can match it except maybe Hornwort. You can treat Guppy Grass as a set and forget plant if you wish. Simply place a few stems or a bunch into the sand or gravel and let it do its thing!

As mentioned above, Guppy Grass also does very well as a floating plant. Especially in fish tanks where there are plenty of dissolved nutrients for it to uptake through its leaves and stems. While it looks a bit untidy the effect is undeniably natural and your fish certainly won’t mind the floating mess!

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Propagating Guppy Grass is as easy as trimming stems into sections. Make sure that you use planting scissors, which are extra sharp. Dull scissors will crush stem tissue, which leads to large patches of rot forming. Once started the plant will struggle to control the spread and may end up dying.

You can allow it to float once trimmed or plant it right away. In either case, roots will begin to form along the cut section that will attempt to anchor into the substrate.

Fertilizer, CO2 & Water Chemistry

Like many stem plants Guppy Grass will uptake nutrients through its leaves and stem just as readily as it does through the roots. This makes having an enriched substrate less important for its long-term health.

I still recommend using one, especially if you don’t intend on fertilizing often. Plant substrates also tend to have a high cation exchange capacity (CEC), which helps them bind to free-floating nutrients so plant roots can get at them.

But Guppy Grass is better than most plants at efficiently extracting nitrogen in the form of ammonia, nitrite, and nitrates from the water column. This makes it an especially effective purifier of the water column, helping to keep your fish and invertebrates healthy.

Guppy Grass also doesn’t require carbon dioxide supplementation but it certainly enjoys it. Like all plants carbon dioxide is the main source of carbon for structural components. CO2 supplements cause plants to really take off and if you’re at all serious about growing plants you should use some. Even DIY carbon dioxide systems offer real benefits over the short and long term!

Carbon dioxide plus moderate lighting will ensure you see dense green growth in your Guppy Grass. In unsupplemented conditions it will still grow well but it will tend to be lanky, growing towards the light and neglecting growth at the base of the stems.

In terms of water chemistry, Guppy Grass is extremely tolerant of a wide range of conditions. After all, this plant is found from Canada to Argentina, covering a wide range of ecosystems. It thrives from room temperature up to tropical conditions (65-78℉). Colder it tolerates well but too much warmth tends to slow its growth.

Guppy Grass grows best in acidic to slightly alkaline conditions (pH 6.0-7.5). However it will still do very well in both more acidic and more alkaline waters. Water hardness is also irrelevant to it – small wonder it’s been in the hobby for so many decades!

Treating New Guppy Grass

When buying Guppy Grass and other fast, densely growing plants, you should be very wary about hitchhikers. Many people selling Guppy Grass grow it in outdoor ponds or in aquariums where snails and algae thrive.

Unfortunately, when you buy Guppy Grass, there is an excellent chance there are snails, snail eggs (which are often transparent and nearly invisible), algae, and other unwanted pests.

That’s why I always recommend sanitizing incoming plants from sources you aren’t 100% certain of. While it sounds complicated a brief bleach soak is all you need to take care of any pests that may be attached. Here’s how it’s done!


  • Unscented Bleach
  • Disposable Gloves
  • Two Buckets
  • Water Dechlorinator (same as you’d use for water changes)

Make sure that your bleach is unscented as the scented agents may be toxic to fish and might not rinse off. Simply mix 1 part unscented bleach to 20 parts tap water. Then give the solution a nice stir with your gloved hands so the bleach is evenly distributed.

Now we add our new plants. Fine-leaved plants like Guppy Grass can uptake the bleach very quickly so we need to limit our exposure to 1-2 minutes maximum. For broad leaved plants like Amazon Swords we can add 30 seconds-1 minute, and another 30 seconds-1 minute for tough leaved plants like Java Fern or Anubias.

Once the timed soak is complete, give your plants a rinse under tap water for 30 seconds to 1 minute. Afterwards, move the plants to your second container that has an extra helping of water dechlorinator.

Since you likely filled it with tap water, you’ll want to add 3-5x the recommended dose as the chlorine in tap water will use up some of the dechlorinator. Let your plants sit for 1-2 minutes. At this point any exterior hitchhikers should have been killed by the bleach and your plants are safe to be introduced into your tank!

Aquascaping with Guppy Grass

Guppy Grass grows fairly tall and bushy, making it a middle to background plant for most aquariums. I don’t recommend using it in nano tanks because it simply grows much too tall and thick. You’ll lose sight of your fish in an aquarium under 10 gallons.

If you use medium to high lighting you’ll be rewarded with more compact growth if left rooted. Guppy Grass is still a greedy plant so you’ll need to trim it back every so often to keep it from shading out its neighbors. The trimmed stems can be left to float, tossed out, or be replanted for clones of the original plant.

If you want more red out of your Guppy Grass you’ll need to provide more intense lighting. Additional fertilizer in the water column, especially iron, helps bring out the red tones in high light setups. Usually high light + fertilizer = algae so you need to be very careful about how many hours per day and what plants are in this tank.

Fortunately, fast growing plants like Guppy Grass ensure that the nutrients get soaked up and used before algae can get a hold of them. When growing high light and fertilized it’s essential to run carbon dioxide, though. Algae can grow with the barest trickle of CO2 but plants, even Guppy Grass, will be severely limited without it.

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You may find it difficult to root Guppy Grass in gravel if it has been previously floating. In this case, you’ll need some lead plant weights to hold it in place.

Guppy Grass is most famous for its uses as a fish breeding ground! Back before aquarium plants were so easy to come by and aquascaping became mainstream, Guppy Grass was one of the few things available. It’s a native plant that grows quite lush yet requires no special lighting, fertilizer, or carbon dioxide.

Baby fish like Guppy fry love hiding among the dense tangles that form, protecting them from their hungry, forgetful parents. Egg scatterers also love Guppy Grass. These fish include Tetras, Killifish, Goldfish, Barbs, Danios…Most fish that don’t provide parental care (Bettas, Cichlids, Gouramis, etc).

I recommend using Guppy Grass in breeder aquariums where you want a bit of cover and spawning material for the adults but nothing high maintenance. The same goes for quarantine tanks for new or sick fish. 

Many aquarists and breeders use bare aquariums for these speciality tanks. However this causes fish additional stress and may even discourage them from breeding. Even a handful of floating Guppy Grass helps uptake additional nitrogenous waste and provides some cover to help fish feel comfortable.

If your fish are egg scatterers they will eventually spawn in and among the Guppy Grass. Once they’ve laid their eggs you can remove the adults and leave the plant in place. Live plants also tend to cultivate biofilms that in turn feed infusoria and other microorganisms.

When your baby fish hatch and move to the free swimming, feeding stage, the Guppy Grass will provide a ready buffet of tiny prey for them! Baby shrimp, snails, and other invertebrates also find Guppy Grass to be a comfortable place to hide and grow.


Aquarium plants are often thought of as expensive, difficult to maintain, and ultimately “not for me.” Guppy Grass turns these assumptions on their head as it’s inexpensive, easy to grow, and useful in nearly any aquarium.

Not only that, it looks beautiful as well. While it grows much prettier when given ample light and nutrients it still maintains a graceful, feathery look that will beautiful any aquarium you place it in!

Image Credit:

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

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