Guppy grass (Najas guadalupensis) is a fast-growing aquatic plant species commonly known by the names – Common water nymph and Najas grass. It is popular in the aquarium hobby for its use in guppy tanks by beginner, intermediate and expert aquarists.
Guppy grass provides the best hiding spots for fry, and adult fish like to swim around it. This plant is fairly hardy and versatile. It can be floated in the water column or rooted in the substrate, and it can thrive without CO2 injection as well.
If you are considering adding Guppy grass to your tank, then you will definitely find this article helpful. This article provides a lot of information about Najas grass; these include background information about this plant, how to plant and care for it in an aquarium.
Quick Notes about Guppy Grass
| Common Name | Guppy grass |
| Other Names | Najas grass, Common water nymph |
| Scientific Name |
Najas guadalupensis |
| Difficulty | Easy |
| Lighting | Low to Medium |
| Optimal pH | 6.0 – 8.0 |
| Optimal GH | 2 – 20 |
| Optimal Temperature | 20 – 26 °C (68 – 79 °F) |
| Substrate | Not needed (or any) |
| Growth Form | Stem |
| Growth Rate | Fast |
| Placement in Tank |
Floating |
| Size | Up to 90 cm (~3 feet) without trimming |
| Fertilizers |
Not needed to low |
| CO2 | Not needed to low |
| Propagation | By clipping the stems off |
| Color |
Light green to dark green |
Origin and Taxonomy of Guppy Grass
Guppy grass belongs to the genus Najas, the water nymphs or naiads. It is a genus of about 40 aquatic plants which are cosmopolitan in distribution. This genus was first described by Carl Linnaeus in 1753. The ‘APG II system of plant classification 2003’ placed the genus Najas in the family Hydrocharitaceae, previously Najadaceae. Guppy grass can be scientifically classified as follows:
Kingdom: Plantae (The Plant Kingdom).
Clade: Tracheophytes (A large group of plants that are defined as land plants, they possess lignified tissues for conducting water and minerals within the plant.
Clade: Angiosperms (A group of flowering or seed-producing plants).
Clade: Monocots (A group of flowering plants characterised by having seeds which contain only one embryonic leaf otherwise known as cotyledon).
Family: Hydrocharitaceae (A flowering plant family including 16 known genera with over 130+ known plant species)
Genus: Najas (A genus of aquatic about 40 aquatic plant species, also known as the water nymphs or naiads).
Species: Najas guadalupensis (A species of the genus Najas).
Habitat of Guppy Grass
Guppy grass is native to North America where it is widespread, it is also distributed in Canada, Mexico, Central America, the Carribbeans, South America, and lastly, Asia.
Guppy grass can be found in a wide variety of aquatic habitats in the wild, such as fast-moving to still streams, ditches and ponds, freshwater, and brackish lakes. It can also be seen growing in local waterways and canals, it is considered as an invasive species in some countries.
Description of Guppy Grass
Guppy grass is an annual submerged plant, it has slender stems which are very long and has many branches. This plant is capable of attaining a maximum height of 90cm (35 inches, ~3 feet).
Najas grass has narrow, thin, flexible leaves, up to 3 centimeters long and 1-2 millimeters wide. Leaves are green colored and arranged oppositely on the stem in whorls, they are edged with tiny unicellular teeth. Guppy grass also possesses white roots and small inconspicuous flowers.
Tank Requirements and Water Parameters
Tank size:
Guppy grass can be kept even in nano tanks. However, because of how fast it grows I would say that a minimum tank size of 10 gallons (~40 L) should be used to house this plant.
Water type, Temperature, Hardness, and pH:
Temperature: Optimal temperature conditions for growing guppy grass is 20 – 26 °C (68 – 79 °F). It is tolerant of a wide range of temperature conditions though.
pH: The ideal pH values for guppy grass is between 6.0 – 8.0.
Hardness: Guppy grass can easily tolerate soft or hard water. Water hardness tolerance range is between 2 – 20 GH.
Substrate:
Guppy grass is mainly a floating plant, however, it can be rooted in a variety of substrates as well. It does not require a nutrient-rich substrate for that.
Regardless of your choice of planting, ensure there are sufficient nutrients in the tank water to properly support its growth.
Lighting:
Guppy grass will do well in low – medium lighting conditions, and ideally, the lights should be kept on for at least 8 hours and 12 hours maximum daily.
In addition, low lighting may be okay for growing Guppy grass, but you should equally know that the more light (closer to medium) it has, the greener it will be. Under high light it gets reddish tint. Keep in mind that, high lighting might also burn Guppy grass.
Read more about it in my article “Advanced Guide to Planted Tank Lighting”.
Fertilization and CO2:
Guppy grass can thrive without CO2 injection, but you can dose liquid carbon if the plants are struggling.
Fertilizer application is essential because it helps to replenish lost nutrients in the tank water. In this case, I would recommend the use of liquid fertilizers from time to time.
Note: Even if Guppy grass was planted, there is no need to use rood tabs. This plant consumes nutrients mainly from the water column.
Important: If you keep shrimp in the tank with the Guppy grass, I would highly recommend reading my articles:
CO2 in a Planted Tank Guide
CO2 in a Shrimp Tank
How Copper Affects Dwarf Shrimp
Shrimp Safe Plant Fertilizers
The point is that a high level of CO2 and Copper (most fertilizers contain copper) is extremely dangerous to the shrimp.
Water flow:
The plant will flourish in the tank in lower flow conditions. That way it grows better, it will not clog your filter and make a mess of your tank as it does when kept in fast-flowing water.
Planting and Propagation of Guppy grass
Guppy grass can be introduced to the tank in two ways:
- choosing to plant it in the substrate
- float it in the water column.
Although, most aquarists prefer to leave it floating in the water as opposed to planting in the substrate.
If you choose to plant in the substrate, then you have to divide the stems into many pieces and root them deep (2 inches or 5 cm) into the substrate, endeavor to space them properly. Guppy grass does not have a strong root system; it serves mainly for plant attachment.
Note: There is also a chance that Guppy grass will melt if you decide to plant it after it has been floating.
Whereas if you choose to float, divide the stems equally and place them in the water column.
You can as well have a mix of both, plant some and leave others floating in the nutrient-rich tank water. The plant’s means of propagation is by sending off side shoots and you can equally clip the stems off and plant or leave them floating.
Care and Maintenance of Guppy Grass
Maintaining guppy grass is simple, putting in consideration that all you need to do is to keep it in check and ensure that it doesn’t overrun the tank. They pose a big threat of cutting off light penetration to plants at the bottom and it’s your duty to avert it by trimming them every few weeks. You either trim the plants for outright disposal or hand it over to fellow hobbyists for planting in their tanks.
Asides that, you should endeavor to supplement the tank water with liquid fertilizers after water changes or during a condition where nutrients may be found lacking.
Trimming is pretty important. The lower sections of the stems become unattractive as they age, so they should be removed periodically.
Benefits of Guppy Grass
Shelter: Guppy grass provides a lot of hiding spots and shelter for fry, hence keeping them safe from predators.
Removal of excess nutrients: Guppy grass helps to maintain good water quality by removing harmful toxins like ammonia, nitrates and nitrites, and other heavy metals.
Breeding: It provides an ideal breeding ground for shrimp, livebearers, and egg scatterers where they can lay eggs and nurture them.
Food source: It also serves as food for herbivores or plant-eating species like Silver dollar, herbivorous Cichlids and Goldfish.
Algae control: Guppy grass helps to reduce algae growth in the aquarium, they will most likely outcompete the algae for nutrients and this will significantly affect its growth.
Oxygenation: It promotes oxygenation in the tank.
Aesthetics: Guppy grass improves the aesthetics of an aquarium; its beautiful dense green foliage is an impressive addition to tanks, it makes your aquarium look more natural.
Foraging place: Guppy grass will be an additional place for the growth of biofilm, which is an ideal first food for newly hatched fry and shrimplets.
Problems Associated with Guppy Grass
Fast growth/ Overgrowth: The common problem you will face while growing this plant in the tank is it trying to overrun the tank due to its rapid growth rate.
Light penetration: The plant’s dense mass if left unattended can block light penetration, thereby preventing light from getting to plants at the bottom of the tank. Ensure to always trim Guppy grass and dispose of the cuttings properly so that it doesn’t block local waterways and canals.
Note: However, it can be also beneficial if you have plants that prefer to have low light. You can read more about them in my article “Top 10 Low Light Aquarium Plants. Pros and Cons”.
Easily breakable: The stems are pretty fragile and easy to break.
Note: However, it is more of a mess problem than anything else because the broken part will develop new side shoots and you will get another plant.
Melting: You might also experience Guppy grass melting after obtaining and introducing the plant into the tank, this may be due to a change in its growing conditions. In this case, it needs time to recover and adapt to the new habitat.
You can also read “How to Spot Nutrient Deficiencies in Aquatic Plants”.
Guppy grass and Tankmates
Although as the name implies, Guppy grass is best suited for Guppies. It is also a great choice for any community tanks that inhabit:
- Small freshwater fish species like Otocinclus Catfish, Pygmy Cory Catfish, Ember tetra, Neon tetras, Green fire tetra, Cardinal fish, Celestial Pearl danios, Zebra Danio, Platies,
- Dwarf shrimp (Red Cherry Shrimp, Blue Velvet Shrimp, Snowball shrimp, Crystal Red Shrimp, Caridina cf. babaulti, Blue Tiger Shrimp, Malawa shrimp, Blue Bolt shrimp, Amano shrimp, Ghost shrimp, Bamboo shrimp, Vampire shrimp, etc.). Basically, you can keep any shrimp species with it. They will love to graze on Guppy grass and hide in it.
- Snails (for example, Ramshorn snails, Nerite snails, Malaysian Trumpet snails, Japanese trapdoor snails, Mystery snails, etc.).
Guppy grass is compatible with most plant and animal species that prefer low lighting. However, some snail species and herbivorous fish like Plecos, Goldfish, Cichlids, Rosy barbs, Sliver dollars, and Tilapia are likely to feed on this plant.
Guppy grass will be a good choice for freshwater crab and crayfish tanks. These animals are notorious for being very destructive in planted tanks. However, in this case, it should not be a problem.
Buying Guppy Grass
Najas grass is inexpensive and readily available in local pet stores, you can source them online as well but it comes at an expense.
The plant does not ship well due to its delicate nature and it can get disintegrated while in transit, it is better you obtain them yourself, that way you are guaranteed of safe delivery.
Quarantine Guppy Grass
Unless you are completely sure that the plant is safe, for example, it was grown in sterile/laboratory conditions (in vitro) and in vitro pot is not damaged or opened, do not forget to quarantine and disinfect Guppy Grass first with bleach or potassium permanganate to avoid the risk of contamination.
- The plant can have parasites, pests like snails, or even predators (dragonfly, damsefly nymphs, etc.).
- It could also be treated with chemicals (pesticide) to remove parasites, snails, etc. However, these chemicals are extremely poisonous to fish, shrimp, and other invertebrates.
To find out more, read my articles:
How to Remove Snails from a Shrimp Tank.
How to Quarantine and Disinfect Aquarium Plants.
Pesticides in Shrimp Tanks. Plants Quarantine.
In Conclusion
Guppy grass or Najas grass is one of the easiest plants to grow in an aquarium. This plant does not need CO2 injection for its growth, this may sound odd- but it can equally grow without fertilizers too. It is an excellent choice for beginners and advanced aquarists, it is undemanding and adds a lot of benefits to your aquarium.
Guppy grass grows rapidly and densely; while you trim it, ensure you dispose of them properly in plastic bags to avoid blocking local waterways. That’s all you need to know about Guppy grass, why not go ahead and get some for your aquarium?
