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Index –

· Introduction

· Example

· Reasons they become invasive

· Which species are not so invasive

· Commonly asked for invasive species


When floating plants become invasive, they can disrupt the natural balance of aquatic ecosystems. They can block sunlight from reaching submerged plants, deplete oxygen levels in the water, and create stagnant areas that are unfavourable for fish and other organisms. It is crucial to be aware of the potential invasiveness of floating plants and take precautions to prevent their spread, especially by irresponsible hobbyists. Responsible management and disposal of these plants are important to prevent their introduction into natural water bodies, where they can cause harm to native flora and fauna.


Hartebeespoort Dam serves as a great example of the presence of invasive floating plants, particularly water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes). These plants have formed dense mats on the water surface, covering large areas of the dam. The proliferation of these invasive plants has had several negative impacts, including:

Ecological Disruption: The dense mats of floating plants block sunlight from reaching submerged plants, inhibiting their growth and disrupting the natural balance of the aquatic ecosystem. This can lead to a decrease in native plant biodiversity and alter the habitat structure for aquatic animals.

Reduced Oxygen Levels: The extensive coverage of floating plants can lead to reduced oxygen levels in the water. As these plants decay, they consume oxygen during the decomposition process, leading to hypoxic conditions that can be harmful to fish and other aquatic organisms.

Water Flow Impediment: The thick mats of floating plants can impede the natural flow of water in the dam, resulting in stagnant areas, reduced water circulation, and increased sedimentation, which affects the overall health of the ecosystem.

Recreational Interference: The presence of invasive floating plants can hinder recreational activities such as boating, fishing, and swimming. The dense mats can tangle in boat propellers and fishing gear, making navigation and fishing difficult.

Reasons Floating Plants Are a Problem:

Floating aquarium plants can be invasive due to several factors:

Rapid Growth: Floating plants are known for their fast growth rates. They have efficient nutrient uptake capabilities and can quickly spread across the water surface, outcompeting other plants for resources.

Reproduction: Floating plants often reproduce through vegetative propagation, where fragments of the plant can break off and grow into new plants. This method of reproduction allows them to spread rapidly and establish dense populations.

Adaptability: Floating plants are highly adaptable and can thrive in various water conditions. They can tolerate a wide range of temperatures, pH levels, and lighting conditions, making them resilient and capable of invading different ecosystems.

Lack of Natural Predators: In many cases, floating plants may not have natural predators or herbivores in the new environment where they are introduced. This absence of natural checks on their growth allows them to multiply unchecked and dominate the ecosystem.

Alternatives to Invasive Floating Plants:

Instead of using invasive floating plants, consider using alternative options that are less likely to cause harm to the environment. Some examples include:


Lagarosiphon major: This is an indigenous floating plant that is readily available and can be used as a suitable alternative.

· Ceratopteris thalictroides, Ceratopteris pteridoides and Ceratopteris cornuta

are plant species tha have the capability to grow as floating plants. Among them, I have a personal fondness for Ceratopteris pteridoides. During the summer, we typically have these plants available. However, due to limited space, we are unable to produce them during the winter months. It's worth noting that among these species, all the Ceratopteris sp. forms fully floating leaves, qualifying it as a 100% floating plant. The rest of the species mentioned here tend to float just below the water's surface.

· Mayaca fluviatilis and Mayaca sellowiniana: These plants can float but prefer to be anchored. They can be used as substitutes for invasive floating plants.

· Potamogeton crispus and Potamogeton schweinfurthii: These plants can float but also prefer to be anchored. They can serve as suitable alternatives in your aquarium.

The most common species we are asked for, that are invasive

· Water Hyacinth (Eichhornia crassipes) -

· Water lettuce (Pistia stratiotes) -

· Red water fern (Azolla filiculoides) -

· Tropical red water fern (Azolla microphylla) -

· Australian Water Clover (Marsilea mutica) -

· Canadian Water Weed (Elodea canadensis) -

· Dense water weed (Egeria densa) -

· Spiked water milfoil (Myriophyllum spicatum) -

· Tropical water fern (Azolla cristata) -

· Water poppy (Hydrocleys nymphoides) -

· Red Root Floater (Phyllanthus fluitans) - (Dirk – dwarf Catfish answer)

By choosing non-invasive floating plants, we can prevent the spread of harmful species and protect our water resources. Let's be responsible hobbyists and contribute to the preservation of our aquatic ecosystems.

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