Guppy Grass Care: Planting, Growing, and Propagation

Guppy Grass is a common, newbie-friendly plant that many aquarists end up putting in their aquariums. While it will survive with basic care, a little bit of knowledge can help it thrive in your tank. 

Read on and learn the ins and outs of Guppy Grass care!

guppy grass


Guppy Grass Fast Facts

  • Common Name: Guppy Grass
  • Other Common Names: Guadalupe Najas, Najas Grass, Southern Waternymph
  • Scientific Name: Najas guadalupensis
  • Plant Type: Floating Stem Plant
  • Natural Habitat: Streams and Ponds in North America
  • Care Level: Beginner

What is Guppy Grass?

Guppy Grass is the aquarium trade name for Najas guadalupensis, a common sight in ditches and ponds across the United States. When found in the wild it’s often called Waternymph or Najas Grass depending on the region.

The plant itself is a stem plant that does well floating. It puts off small stems with tightly packed, tiny leaves that give it an interesting texture.

The one thing to keep in mind about Guppy Grass is that it’s considered an invasive species. Much like Elodea densa, it grows quickly and easily without much intervention needed. It can quickly grow to clog waterways when left untended.

You shouldn’t be letting any plants end up in the wild, but an invasive plant classification invariably means a plant is easy to grow. In this case, Waternymph is common enough that most of us have seen it in the wild.

It also means the plant is fast growing in most cases.

Since Guppy Grass doesn’t need to be rooted, it can grow amazingly fast. There are no real limitations to how much it can grow other than the nutrients in the water.

All of this makes it ideal for being kept in private aquaria. Most people have more trouble getting rid of Guppy Grass than keeping it alive. The fast-growing nature of the plant also means it pulls a lot of nutrients from the water.

So, we’re left with a plant with the following qualities:

  • Very Hardy
  • Fast Growing
  • Doesn’t Need to Root
  • Survives in a Wide Variety of Conditions

So, right from the start, we have a plant that’s perfect to stick in a tank. Without proper care, it’s likely to survive, but the growth won’t be as dense or attractive. It’s thriving that we should aim for as aquarists.

What Kind of Aquaria is Guppy Grass Right For?

Guppy Grass may not fit in every aquarium, especially planned planted tanks. It’s rapid growth and hardiness can make it a problem if you’re not careful to control it.

On the other hand, Guppy Grass is perfect for other applications.

It’s worth a look for the following situations:

  • Single Plant Tanks- Guppy Grass is very low maintenance when kept alone, just trim and discard as you need to. If it’s not going to harm other plants you’re free to let it grow into a dense mat and create a jungle.
  • Breeding Tanks- Guppy Grass is a good choice for breeding livebearers, and it can be used as the sole plant in a tank. Just throw it in and let the tank cycle, Guppy Grass will grow in and create a protective mat.
  • Low Light Dutch-style Tanks- Careful trimming can turn a couple of stems of Guppy Grass into a thick shrub. In high light situations, it may grow too quickly.
  • Low Tech Planted Tanks- Low tech tanks keep growth at manageable levels for the most part. They can be a great floating option.
  • Brackish Tanks- Your plant choice is very limited in brackish tanks, Guppy Grass grows well in those conditions. It’s a big advantage for those who like Mollies and Puffers.
  • Shrimp Tanks- Not everyone has the time for a carefully planted garden, and Guppy Grass can give shrimp everything they need from plants without requiring a lot of fiddly maintenance.
  • Low Tech Community Tanks- Not every tank with plants is a planted tank. Guppy Grass is a good plant to throw into a community tank just to give some cover. Since most community tanks have moderate light and no CO2 the plant can just be trimmed regularly.

Care Overview

Guppy Grass is a very beginner-friendly plant. There are only a few spots that a newbie might get tripped up.

Most of the following are good general guidelines for any planted tank, so keep reading!

Ideal Water Conditions

Guppy Grass is in an “anything works” situation with water. It survives in a wide variety of different temperatures, pH, and hardness levels. It’s an adaptable plant.

In general, if a tank is tuned for any fish the parameters will allow the plant to grow. Guppy Grass tends to thrive in water from 65-75°F and a pH of 7. You can go pretty far from that happy middle and still enjoy a lot of success.

One thing to keep in mind: Guppy Grass sometimes “melts” when changing water conditions. It’s not a big deal, just remove as much of the decayed foliage as you can from the tank. It’ll begin growing from the stems again in short order.

Guppy Grass is a great nitrate scrubber due to its high growth rate. It’s not going to replace a filter, of course, but it’s a solid pick if you have issues with high nitrates in your tank.

Light and CO2

Guppy Grass doesn’t need high lighting or CO2.

In fact, I recommend against using high lights or CO2 on a tank with Guppy Grass if you don’t like tank maintenance. The plant itself gets thicker and brighter, but it grows out of control in these conditions.

If you do opt to use it in a high-tech tank, you can expect to trim at least once a week. In some cases, daily trimming may be required as Guppy Grass grows fast.

A simple 1W/50 Lumen per gallon light is enough for the plant to thrive, and you can use a liquid CO2 booster like SeaChem’s Excel to get a boost in growth. You’ll rarely need liquid fertilizers for this plant, but it’s not a bad idea to use them if you have other species in the tank.


You don’t need fertilizers if you just have Guppy Grass. That’s rarely the case in a planted tank, instead, you’ll have a bunch of different plants.

I’d skip the fertilizer in a tank with just Guppy Grass. A breeding setup, for instance, with a couple of handfuls thrown in and allowed to grow out.

If you have other plants to fertilize it won’t do any harm. Root tabs are useless, even for planted specimens, and not something to be concerned about.


Propagating Guppy Grass is really simple: you clip it with a pair of sharp scissors. You now have two plants! Drop them back in the tank and you’re good to go.

On the other hand, there is a better way than snipping at random. Like most stem plants, you can create a bushier Guppy Grass stem by carefully planning your cut.

The ideal place is just above a growth node. This causes the plant to put out two stems to replace the lost portion, and you can create a dense bush in a few weeks’ time. You can also snip the cutting next to a node on both ends.

Be wary of cutting too many stems and leaving them in the tank. Often beginners will try to maximize their plant growth by placing as many stems as possible.

That works very well, but you need to remove whole stems to thin out the growth as time goes on. Two stems and twelve stems can have the same mass, but the twelve stems will grow exponentially faster.

Float or Plant?

Guppy Grass gives the impression of something growing from the bottom of the tank, but it actually does the best when left floating. 

In fact, even the planted stems will pick up their nutrients from the water column.

Najas guadalupensis grows a bit differently when planted or floating. It’s a neat trick that seems to be designed to gather the most light depending on the situation. It’s a cute trick, but it sometimes trips newbies up.

The plant will almost always melt if you plant it after it’s been floating or vice versa. It has to adapt to the new situation, so it sheds its foliage and begins growing again. 

Often it will only begin growing from the tip of the cutting. Keep them small for planting purposes.

There’s some good news if you want to plant Guppy Grass: you can use an inert substrate and it will grow fine. You can even use plant weights to hold it on the bottom of the tank.

While it seems to last longer than Elodea densa, planted Guppy Grass often separates just above the substrate as it rots under the substrate. Don’t worry if you suddenly find some bits floating, re-plant them and remove any visible bits that previously held the plant down.

The real problem with this plant is usually overproliferation. It can grow very thick in a short period of time in many tanks, don’t be afraid to remove a handful or six to thin it out.

What About Brackish Tanks?

Here’s my favorite part about Guppy Grass: it makes a good floating plant for brackish tanks. It just happens to be among the hardy plants that don’t mind a bit of salt.

In some cases, growth may be a bit slower but that’s rarely an issue.

This makes Guppy Grass an ideal plant for any breeding tanks that have brackish fish. Mollies, for instance, will appreciate the dense cover for their fry. Since it’s floating, you can also use it in bare bottom tanks for more efficient breeding setups.

Disposal After Trimming

Do not throw your trimmings where they can reach native waterways.

Ideal disposal would involve letting the plant dry out for an afternoon then tossing it in the trash can. You can throw cuttings down on your back patio or another flat area during the day. It’ll only take a few hours to dry out.

In any case, just don’t let it get into native waterways. It’s invasive in many areas and after you have some experience growing it… well, you’ll see why this can be a big problem.

How to Use Guppy Grass in Aquascaping

Guppy Grass is usually a dominant force in tanks it’s introduced to. A few handfuls in a 10-gallon tank can turn it into a dense jungle inside of a month with a bit of extra care.,

As a floating plant, it needs a gentle hand and a lot of maintenance to be much more than a bundle of plants to the tank’s profile. On the other hand, planted Guppy Grass can be used like any other stem plant.

Since it can be trimmed to branch repeatedly it makes a good “shrub.” In Dutch-style aquaria, it can be great in the mid-ground or in the back of the tank. Dutch-style tanks already require frequent pruning, so it’s not a bad choice.

In free-growing “jungle” tanks it can be problematic. The quick growth can choke out slower-growing plants.

Where it gets interesting is building a tank around Guppy Grass and small fish who will enjoy it. A little bit of hardscape, a good-looking substrate, and a handful of Guppy Grass is enough. This creates a dense jungle that many fish enjoy, and maintenance is as simple as thinning out the floating plant.

Overall, I’d skip Guppy Grass if you’re into carefully planned aquascapes but it’s a great choice if you want a low-maintenance jungle tank.

Controlling Guppy Grass

Guppy Grass is low maintenance in low-tech tanks. You just let it grow and trim it when it starts looking too thick, usually once a week or every two weeks depending on water conditions. It will survive, and one of the tricks to keeping it is learning to limit its growth.

It’s a bit of an odd concept for those who’ve proven not to have an aquatic green thumb in the past.

When you place Guppy Grass in the CO2-rich, bright water of a high-tech setup you can be looking at unbelievable growth. Like, daily growth measured in inches.

And that’s each stem growing a couple of inches each day.

In a brightly lit tank with CO2, controlling Guppy Grass can become a daily chore. Make sure that you’re willing to commit if that’s your plan.

Fast Growing, Hardy, and Prolific… It’s Guppy Grass!

Guppy Grass is a great plant for newbies, especially since the main challenge is just keeping it from overgrowing the tank. Once introduced, it’s a great source of cover.

It’s a solid choice if you’re a beginner, just make sure to put the above information into action!