Guppy Grass (Najas Guadalupensis)

Growth Rate:Fast
Light Demand:Low To High
CO2 Demand:Low

Najas Guadalupensis also is known as “southern water nymph”, “common water nymph”, “najas grass” or “guppy grass” is an aquatic plant species belonging to the Najadaceae family. Even though the origin of this plant is Canada (from Alberta to Quebec), it could also found in the natural wetlands of Central America, the United States, Mexico, South America and West Indies. Additionally, it has been introduced to the natural water resources in Japan, Palestine and Israel.

Najas Guadalupensis that is quite similar to Nodding Water Nymph and Slender Water Nymph, differs from them only with minimal differences. This fast-growing plant species is a source of interest for aquarists of all levels and in the wild, ducks and waterfowls feed with the leaves and seeds of this plant. It also promotes high oxygenation in the aquariums.

Najas Guadalupensis, which contains different shades of green and has thin stems, creates the appearance of grass with leaves ranging from 1-3 cm in height and about 0,5 cm in width. This plant blooms with small green flowers in summer (especially from June to August) also has fruits that are 3 mm long and consist of a single seed. Depending on the environmental conditions, they can reach overall sizes between 30-90 cm.

Najas Guadalupensis could be used to add a nice ambiance to the aquarium as well as food for herbivorous cichlids, a swimming area that adult fish will love or shelter for dwarf shrimps and fish fry.


Water with a pH of 6,0 – 7,0 and a temperature of 20-28°C are suitable conditions for the growth of this plant. This species, which can live under different light intensities from low to high but it displays a greener appearance at high-intensity light. However, it should be kept in mind that high-intensity light can cause burns to the plant close to the water surface. It can also live in tanks with such very small dimensions, but it is more appropriate to choose tanks of approximately 40 liters due to its rapid propagation. It can adapt to both hard and soft water and thus it can live in a wide range of water hardness. Carbon dioxide injection is not necessary for the growth of this plant but dosing fertilizer especially with macronutrients is important to support continuous and healthy growth. According to some reported cases, better growth of this plant has been observed in low flow waters.

Easy propagation and rapid growth can bring some problems to the tank. One of these is fast and the overgrowing of the plant could create an aesthetics problem in the tank. On the other hand, the main and most important problem is that overgrowing creates a light penetration problem. This problem can be annoying if there are other plants desired to be grown in the aquarium. In case Najas Guadalupensis is left to its own, it will overgrow and prevent other plants’ development. But, regular trimming of some parts of the plant can solve both of these problems. The plant can easily propagate by clipping.

In summary, it is a plant species that is frequently preferred by aquarists due to its natural appearance in the aquarium, providing a good habitat and food for some fishes, shrimps and fry, also promoting oxygenation and increasing survival rates of fry.

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