Many aquarists, noticing small green leaves on the surface of the water, immediately begin to worry. They see duckweed as an annoying weed that quickly covers the entire water surface, shading plants and changing the microclimate in the aquarium. Indeed, this tiny floating grass can become a real challenge if left to grow unchecked.
However, there is another side to this coin. Duckweed is a living natural phenomenon that can be very beneficial to your underwater world. It serves as an excellent natural filter, absorbing excess nutrients and helping to control algae. For many fish and shrimp, its delicate roots provide additional food and shelter.
So what is the truth? As is often the case, the answer lies somewhere in the middle. It all depends on your goals and your ability to manage this plant. Let's figure out how to turn a potential pest into a valuable helper by controlling its growth and using its strengths to balance your aquarium.
Distribution
Duckweed belongs to the Araceae family and is found all over the world except Antarctica. Thanks to its unpretentious nature, it can live in freshwater bodies with slow-flowing or stagnant water – sometimes even in puddles that do not dry out for long periods of time. The plant particularly likes ponds and lakes in warm regions, where a layer of duckweed can reach several centimeters thick on the surface.
Cultivation and care
Many aquarists consider duckweed to be a common weed. Shoots can indeed get into the aquarium accidentally, but they do not always cause harm. The plant serves as a biological filter, saturates the water with oxygen, provides inhabitants with useful substances, and absorbs excess organic compounds.
Duckweed requires virtually no care and, under favorable conditions, reproduces very quickly and without outside intervention. It serves as an excellent shelter for fish, especially labyrinth and livebearing fish—aquarium inhabitants will enjoy building nests in dense thickets.
Water parameters for ideal maintenance
Duckweed grows well at temperatures between 12 and 30 degrees Celsius. Acidity is practically irrelevant, but excessive fluctuations should be avoided. The plant can adapt to pH levels between 5 and 8, but if the pH is too low or too high, it will stop growing and may die. Hardness is also not particularly important, but it is not recommended to exceed a value of dH 10-12°.
Duckweed grows best in aquariums with clean water. If the water is heavily polluted, the plant will not be able to perform its filtering function properly, and particles of turbidity and organic waste will settle on the leaves and hinder growth. At the same time, filters should not create a strong current – it should not be forgotten that duckweed prefers stagnant or slow-flowing water.
Duckweed cannot tolerate salt or chlorine, even in small quantities. At minimal concentrations of these substances, it stops growing, and at high concentrations, it dies.
Duckweed is a small floating plant that many people associate with annoying weeds, especially when it quickly covers the entire surface of the water. But in fact, it can be useful: it cleans the water of excess fertilizers, provides shelter for fry, softens the light, and reduces the growth of truly harmful algae. The main thing is not to let it grow uncontrollably. In moderate amounts, duckweed is more of a helper than a problem and can certainly take its place in a healthy aquarium.
Lighting requirements
Proper lighting is essential for duckweed growth. The brightness should be at least 0.5 watts/liter, and the duration of lighting should be 10-12 hours. Without light, duckweed can only survive for a few days and stops producing oxygen. Sunlight can also be used, but it is important to ensure that it is diffused, as the plant does not like direct rays.
Soil and substrate requirements
Duckweed lives on the surface of water bodies, with its leaves on the surface and its roots in the water. Accordingly, the substrate for growing the plant is not important—it gets its nutrients from the water, and light triggers the processes of photosynthesis.
Fertilizer requirements
Duckweed does not have any special fertilizer requirements either. Like most other plants, it responds well to CO2 supply—it grows faster and acquires a bright emerald hue.
For duckweed growth, it is better to use fluorescent lamps rather than incandescent lamps. Incandescent lamps cause the upper layers of water to overheat, which impairs plant growth and affects its beneficial properties.
Reproduction
To propagate duckweed, take a small offshoot and keep it separate from the mother bush. After a while, it will take root, begin to grow, and form a separate island.
Duckweed is a very common plant, so it can be collected from the nearest pond or lake.
However, it is not possible to introduce “wild” specimens into the aquarium without a two-week quarantine period, as there is a risk of introducing bacteria, mollusks, or other living organisms that could disrupt the ecological balance.
In defense of duckweed, it can be said that shrimp (especially newborns) feel at home in its intertwined roots. There is plenty of food for them there, and it is completely safe. In an aquarium with fish, shrimp will hardly find a better refuge than duckweed thickets.
— Alexander Tkachuk, marine biologist, expert in aquarium and terrarium keeping
Plant varieties
There are several varieties of duckweed—they differ from each other in appearance, but they are not capricious and undemanding in terms of living conditions.
Three-lobed
The difference between this plant and others is that it floats in the water column and only rises to the surface during flowering. Its leaves are rounded and about 1 cm in size. It has a pronounced seasonal growth pattern—in winter, it is kept in separate containers at a temperature not exceeding 12 degrees Celsius.
Multiroot
The leaves of this duckweed are slightly larger than those of the small variety (6 mm), and they have not one root but a whole bunch of them. They are round in shape, green on top and purple underneath.
Small
The most common type of plant. The leaves are oval in shape, 3-4.5 mm in size, and yellowish-green in color. The underwater part (root) can reach 10 mm.
Humpback
A variety of duckweed that is also common in aquariums and is considered the fastest growing. The leaves are 5-7 mm in size, with a glossy and slightly curved surface.
No special conditions are required for any variety of duckweed. The only thing the aquarium owner needs to provide is bright, even lighting.
So what is duckweed: a malicious weed or a valuable helper? The answer, as is often the case in aquarium keeping, depends on the specific situation and your goals.
If your goal is a perfectly clean, sterile aquarium with a clear view of every stone, then you will definitely not like duckweed. It grows quickly and requires constant monitoring. But if you value naturalness and balance, then it can become an indispensable element.
This modest plant is an excellent natural filter that absorbs excess nutrients and improves water quality. It creates a cozy shelter for fry and timid fish, and for many species, it serves as a useful vitamin supplement to their diet.
Thus, duckweed is neither good nor bad in itself. Everything depends on a competent approach. A small amount of duckweed will be beneficial, while uncontrolled reproduction will cause problems. The main thing is to understand its nature and manage it, rather than fight it. Then this little green carpet will become your faithful ally in creating a healthy aquarium.
