Guppy Grass: Care & Propagation Guide

Guppy Grass (Najas guadalupensis) is a fast-growing species of aquatic plant that has become famous for its bushy growth. Aquarists usually use this plant in their shrimp tanks. Despite being a great plant for shrimp tanks, the guppy grass is not sold very often in pet stores. This is because its fast-growing nature can be a threat to natural lakes and rivers. 

This plant is super easy to care for and will grow rapidly when enough lighting and nutrition are available. They are called guppy grass as they can create dense jungles that guppy fry or other small species can hide and grow. They are also known as southern waternymph, water nymph, Najas grass, common water nymph, or simply as Guppy Grass. 

If tank conditions are not in favor of Guppy Grass they will start to shrink and slowly melt. So it is important to know all about the care requirements of this plant to make sure they thrive in your aquariums. This guide will walk you through all the information you need to know about guppy grass and a few tips and tricks to boost their health and growth.


The Guppy Grass or Najas Grass is native to Canada (from Alberta to Quebec). But will also grow naturally in other parts of America such as the United States, Mexico, the West Indies, and South and Central America. Since its popularity in the aquarium trade, this plant has been introduced to Japan and Israel as well as a few other countries.

The Najas genus, where guppy grass belongs, was first described by Carl Linnaeus in 1753. Since then there are about 40 species identified in the Najas genus. All members of the Najas genus share the same or similar appearance and they mostly live in the same environment. The most famous and commonly used plant in the aquarium hobby is Najas guadalupensis (Guppy Grass).

Guppy grass is most famous for its bushy dense growth that makes them a perfect fit for breeding tanks. It can provide an ideal hiding spot for fry to protect them from larger adult fish. Large adult fish usually avoid dense and bushy areas to avoid getting tangled. This gives the fry an advantage when it comes to growing in a tiny space like aquariums.

They are fairly hardy and versatile aquatic plants that will grow fully submerged and do not need substrate to survive. Because guppy grass is native to colder regions of North America, it can be a great plant for colder aquariums. They will happily live year-round in a pond outside or a cold tank with fish inside. 

They grow rapidly and can take over the available space in a matter of weeks if enough light and nutrients become available for them. This makes them a great plant for shrimps and livebearer tanks to safely grow fry as well as remove ammonia and other toxins from the tank quickly. 


Guppy Grass (Najas guadalupensis)

Guppy grass has bright green leaves growing on its slender branching stems. The stems can grow up to 3 feet in length before it becomes too heavy and breaks into a new plant. The leaves are thin and light can slightly pass through them. Each leaf can grow to about 1.5 – 2 inches in length and about 2 – 3 millimeters in width. 

Guppy grass is one of the largest aquatic plants you can own in your aquarium. But they don’t grow straight upwards. Instead, they will grow twisting and tangling in between other stems and create a bush-looking giant plant. This makes it possible to house this plant in smaller aquariums as well. 

Stems are thick but fragile and will easily break if not handled with care. They also grow small white thread-looking roots that serve as anchors to hold the plant on objects. Roots are not developed to absorb nutrients or to be planted in the substrate. 

They will constantly grow new stems and branch out to become gigantic plants. So it is important to prune this plant regularly to make sure they grow and stay healthy looking. They can also trap debris and waste when they become too dense. This might make them look ugly so regular maintenance is a must to maintain them in a good-looking state. 

Size & Growth Rate

Guppy Grass can grow up to 2 – 3 feet. When they have enough space and light they will grow large and stay dense. The water movements also have a huge impact on the size of this plant. 

Fast-moving waters can break the stems causing the plant to stay small or even die. In a moderate or slow-moving environment like in an aquarium, they will grow to their full size. 

Guppy grass has a very fast growth rate. They can reach their maximum size in a matter of weeks and start to grow new stems and propagate. This makes them a super fast-growing aquarium plant.

Guppy Grass Care

Guppy Grass care is simple and easy. With regular maintenance and creating the balance in your tank in favor of this plant, you can grow them with ease. They are super beginner-friendly plants that can tolerate most tank conditions. If you have a good light source and enough fish to produce waste, guppy grass will thrive. 

Because the balance is super important for keeping guppy grass long-term, you will have to perform a few water tests to make sure your tank is ready for this plant. If there is an imbalance in the water parameter your guppy grass can easily melt in just a few days after bringing it home. 

To prevent this from happening, you will need to follow all the basic requirements mentioned below.

Tank Size

The ideal tank for Guppy Grass is 10 gallons or more. Technically Guppy Grass can grow in any size tank but the smaller the tank the more work you need to do. So it is always recommended to have them in a slightly bigger tank. 

At the same time having them in a super large tank or a pond can become problematic as they grow super fast and can cover the entire available space. This will also increase the amount of maintenance you will need to do. 

Water Conditions 

Fortunately, when it comes to water conditions, the Guppy Grass is not so demanding. Its hardy grass nature will help the plant to live in most aquarium environments. 

Guppy grass appreciates slow to moderate water current. The stems of this plant can easily break if the water circulation is fast in your aquarium. However, a decent amount of water movement is necessary in order to remove debris from the plant.

This plant can live in a wide range of water parameters but it is important to prevent fluctuations. A stable tank that falls within the range mentioned below can be a great tank environment for guppy grass.

  • Temperature: 65 – 82 Degrees Fahrenheit 
  • PH: 6 – 7.5
  • TDS: 60 – 230 PPM

Guppy Grass can tolerate colder water as low as 50 degrees Fahrenheit or as high as 90 degrees in short periods. But it is not recommended to keep them at these extremes as things can easily go wrong and cause the plant to die. 

CO2 Requirement

Guppy Grass does not need CO2. This plant can thrive without CO2 injection and the carbon dioxide produced by fish or other tank inhabitants is usually enough for guppy grass.

However, like all aquatic plants, guppy grass will grow a lot better and healthier when more CO2 is available. Carbon dioxide will help the plant to stay lush green and photosynthesis much better.

Guppy Grass (Najas guadalupensis)


Guppy Grass needs medium to strong lighting conditions. This plant needs a full spectrum of light to be able to grow at its maximum growth rate. 

Some online resources claim that this plant can live in low lighting conditions. It’s either these websites never kept this plant themselves or their definition of low light is different. 

In our experience, this needs a properly planted aquarium light to thrive. It can survive in low light conditions for a short period of time but it will slowly start to melt and eventually die. 

A 4000 – 6700k full spectrum light is the ideal kind of light for Guppy Grass. The balance in your water conditions and the lighting is also important to give this plant an ideal environment. 

You can keep the light on for 6 – 12 hours daily depending on the setup you have. 


Guppy Grass does not need substrate. This plant absorbs nutrition from the water column. They will develop tiny white root-like structures that are used to hold on to objects rather than feed. 

Planting & Placement

Guppy Grass will grow tall and bushy and will cover the entire tank if you don’t prune them. So it is important to place them in the background if you want to keep them in an aquascape tank. 

This plant is mainly being used in breeding tanks and the placement in a breeding tank is not that important. It is definitely possible to plant them in an aquascape but you will need to regularly train them to prevent them from taking over the tank.

Guppy grass is a water column feeder plant. Meaning it will absorb nutrients directly from the water and does not need substrate. So it is important not to plant them in the substrate as the lack of light will cause the stems to rot over time. 

You can leave the plant free floating in the tank or attach it to a rock or driftwood to keep it in place. This is the ideal way of “planting” them in a tank. 

Guppy Grass Propagation

Propagating Guppy Grass is very easy and can be done easily by anyone. You can easily propagate guppy grass by cutting 3 – 4 inches off the main plant. The new cuttings will continue to grow and become new plants. 

Because this plant is super fast-growing, most of the time you will not even have to propagate them manually. Just by leaving them in the tank and providing them with all the elements they need, they will grow and expand. 

Maintenance & Fertilization

Despite being a fast-growing plant, maintaining guppy grass is very easy. If you want to have them in your breeding tanks, like what we do, you will not need to put very little time into the maintenance of this plant. 

Every now and then when the plant grows too large you can simply pull a bunch and let the rest grow. We usually do this every few months and at the time of doing our water changes so it’s barely a hustle. 

However, if you want to keep them in a well-maintained tank or your display tanks you might need to regularly trim the plant to avoid overpopulation. So we highly recommend having guppy grass in a breeding setup rather than in a well-defined and aquascaped display tank. 

It is important to note that Guppy Grass can melt when the tank conditions are not right. This can cause ammonia spikes in the tank or cause cloudy water. This only happens if you have low light conditions or enough fertilizer is not available. 

Generally, guppy grass does not need any extra fertilization. The amount of waste produced by fish is just enough for the plant to grow. But if you want to make this plant grow faster adding fertilizer and co2 can help you with growing them faster.

Tank Mates

This plant became famous as “Guppy Grass” because many breeders use them to breed guppies. But they can live with any fish and invertebrates that are plant-friendly. This plant can live in harmony with most aquarium plants, invertebrates, and fish. 

However, if you have other water column feeding plants, the fast growth rate of guppy grass might cause other plants to suffer. A fast growth rate means the plant will use more nutrition at a faster rate leaving less to nothing for other plants. 

If you have livebearer fish or shrimps that you want to breed then we highly recommend this plant. 

As mentioned, Guppy Grass can coexist with most aquarium species. But here are our top pics of ideal tank mates for this plant:

Benefits of Guppy Grass in Aquariums

Guppy Grass is one of the best ways to create more surface area as well as more hiding areas for smaller fish. They are beautiful and hardy plants that can tolerate most tank conditions. This makes them a great beginner plant to start your aquatic plant-keeping journey. 

The main reasons that this plant is famous are its fast growth rate and dense growth patterns. This solves two big issues in a breeding tank. The guppy grass will extract all the waste and toxins from the tank as it grows and provides the fry a safe haven to hide from the larger fish. 

Guppy Grass (Najas guadalupensis)


Guppy Grass is an affordable and hardy aquatic plant. They can tolerate a broader range of water parameters compared to other species of aquatic plants. This makes them a great beginner plant that most can start their plant-keeping journey with.