Profile of thick-leaved algae

The thick-leaved aquatic algae, Elodea densa, is part of the frog’s bit family and, despite its unflattering reputation, remains a popular choice for aquariums and ponds. Its negative labeling as a parasitic plant likely stems from its ability to form dense, large-scale single-species populations, which can result in ecological issues. These include the displacement of native species and a subsequent decline in local biodiversity. Through the aquarium trade, populations of this so–called neophyte have spread globally, thriving beyond their original habitats and earning a reputation as a somewhat invasive species. Its rapid growth and widespread nature continue to create challenges in Europe, impacting maritime navigation, water management, fishing activities, and water sports. As a result, it is often regarded as a nuisance or even an environmental menace.

However, algae have been intentionally introduced into many areas to help improve overall water quality by increasing oxygen levels, protecting fish stocks, and reducing mosquito populations.

In our profile we have summarized all important information on the origin, appearance and use of seaweed as well as its care in your aquarium or garden pond.

Origin

The original distribution area of ​​the thick-leaved aquatic algae is South America – there Elodea Densa thrives from southeast Brazil to Uruguay and Argentina. Stagnant or slow-moving waters up to three meters deep near the shore offer ideal living conditions.

Due to trade and globalization, the thick-leaved aquatic algae can now also be found outside its original distribution area: for example, it thrives. B. in some parts of Europe also in ponds, ditches and slow-flowing bodies of water such as lakes or artificial dredging basins. It was probably first discovered in Germany in 1914. Here it is considered an invasive plant, but not classified as problematic, as elsewhere.

Appearance and use

The dense-leafed aquatic algae is often one of the typical plants to be planted in the aquarium for the first time and, since it is considered very easy to care for, it is also suitable for beginners in the beautiful hobby of aquarium keeping.

The leaves of Elodea Densa have an elongated, narrow shape and are dark green in color, their stems are up to three millimeters in diameter and have a dense growth of leaves.

The dense-leaved aquatic algae grows quickly by up to ten centimeters per week and is therefore ideal as a background plant in your underwater world, which offers the shy aquarium inhabitants a good place to retreat and hide and can also be used as a spawning place. If you plant your Elodea Densa not in the background, but in the front or central area of ​​your underwater world, it will soon block your view, so you should use other plants that grow less well.

^{Due to its rapid growth, the dense-leaved aquatic algae is particularly suitable as a background plant.}

Due to its rapid growth, the thick-leaved aquatic algae serves as a useful and effective oxygen supplier for the fish and invertebrates in your aquarium. It also absorbs pollutants present in the water and thus counteracts the formation of algae. This makes it a perfect plant for the import phase of your underwater world.

Treatment

Thick-leaved aquatic algae is a hardy, adaptable and easy-care aquatic plant that is ideal for first planting in an aquarium and can usually be easily cared for by beginners.

Water values

As regards water parameters, Elodea Densa proves to be extremely adaptable; only that the water temperature must not be too high and must not permanently exceed the maximum value of 26 °C. Although the light requirement is generally moderate, more intense lighting can lead to denser growth, so that the algae can offer your aquarium inhabitants a variety of interesting hiding places. However, direct sunlight should be avoided. Elodea Densa shows a preference for calcareous water, but also thrives in very soft water, so the pH value is in a tolerance range of 5 to 10.

Plant

If you decide to landscape your underwater landscape with fast-growing aquatic algae, you have two options for letting it grow in your aquarium.

So you can plant them at the bottom of your aquarium or let them swim freely. In order to be able to plant seedlings as easily as possible, you must first separate the individual stems from each other, cut the roots with a sharp knife and carefully remove the leaves from the lower part. Then place the individual stems a good distance from each other.

However, you can also let the young shoots float freely on the water, as they reproduce without contact with the ground and over time form a carpet of floating plants. However, unlike a garden pond, this approach can only be recommended to a limited extent for an aquarium, as the resulting plant mat could shade other plants and impede their growth.

Pruning

Individual shoots of the thick-leaved aquatic algae in the aquarium, if left uncut, can often reach a length of up to half a meter or even more. So that they do not obstruct the view due to their rapid growth and do not completely invade the underwater world, it is advisable to prune them regularly as needed. To do this, you should shorten the sprawling shoots with as clean a cut as possible. This will cause the plant to develop new shoots and give the seaweed a beautiful bushy shape, as the growth of secondary shoots is also stimulated.

Multiply

Propagation of the thick-leaved aquatic algae is generally simple: simply cut a particularly beautiful shoot to a length of about 20 cm and plant it elsewhere in the underwater landscape.

If you notice that the leaves of your aquatic plant are becoming lighter and that individual shoots are thinning or even wilting, this can often be attributed to a nutrient deficiency. In this case it can often be helpful to increase the light intensity or, if necessary, add some fertilizer that is safe for the aquarium inhabitants.

Questions and answers about thick-leaved aquatic algae

1. Is seaweed good for the aquarium?

Waterweed is not only very beautiful to look at in your underwater landscape, but is particularly adaptable and also proves to be extremely useful as it absorbs harmful substances from your aquarium water and thus prevents the formation of algae. It also functions as an oxygen supplier for the fish and invertebrates in your underwater landscape. After all, aquatic algae is not only suitable for your aquarium, but also for your pond: Elodea Densa can grow up to one meter in height and is excellent for keeping the water clear. It is considered easy to care for and is an extremely effective oxygen supplier.

2. What does the aquatic plant need to grow?

The thick-leaved aquatic algae is considered a hardy, easy-care plant that does not require special water parameters and thrives in both acidic and alkaline water as long as the CO2 value is not less than 5 mg per liter of aquarium water. If your algae appears stunted, this could be an indication of a nutrient deficiency, so a special fertilizer or additional CO2 may be helpful.

3. How is aquatic algae optimally cared for?

As a rule, the dense-leafed aquatic algae proves to be an easy plant to care for in your aquarium, but it grows very quickly and can therefore reach a length of up to half a meter or more relatively quickly in your underwater world. Therefore the shoots should be pruned regularly according to the individual growth in your aquarium, carefully cutting off any stems that are too long. Additionally, the dense-leafed aquatic algae requires sufficient light, although direct sunlight should be avoided.

4. What makes aquatic algae special? Why the water plague?

Aquatic algae thrives in both aquariums and garden ponds and is considered an effective oxygen supplier that helps clean water or keep it clear. Elodea Densa also grows very quickly and quickly establishes stable populations in your garden oasis.