Duckweed (Lemna spp.)

Species description

Care, breeding and tankmates

Plant profile

Placement

Floating

This plant is strictly a floating plant that covers the water surface. It naturally spreads across the top, providing shade for the aquarium below. It can be corralled using floating rings to prevent it from covering the entire surface.

Botanical form

Floating

It features small, simple fronds that float flat on the water surface. Thin, trailing roots hang down into the water column to absorb nutrients. The plant reproduces primarily through vegetative budding.

Growth

very-fast

The growth rate of Lemna spp. is extremely fast and often explosive under good lighting. It doubles its biomass in just a few days if nutrients are abundant. Its rapid multiplication requires frequent culling to avoid light blockage.

Substrate

None

Lemna species are true floating plants and have no need for a conventional planted substrate. Their short, hair-like root structures draw all necessary macro and micronutrients straight from the surrounding water. Because they never touch the bottom, the choice of aquarium substrate is entirely irrelevant to their health. They flourish in almost any setup as long as the water column contains sufficient dissolved nutrients.

Column fertilization

Recommended

Liquid column fertilization is highly beneficial as it has no substrate roots. It responds quickly to added macronutrients and micronutrients in the water. Over-fertilization can lead to uncontrollable and rapid surface overgrowth.

Root fertilization

None

Root tabs or substrate fertilizers are completely unnecessary for this plant. All of its nutritional needs are met through its floating roots. It has no connection to the aquarium substrate.

Trimming

Regular

Trimming involves simply netting out excess portions from the surface. It is important to remove a significant amount weekly to maintain light penetration. Ensure no tiny pieces are left if you wish to eradicate it completely.

Propagation

Division

Propagation occurs naturally and rapidly through continuous division. A single small frond will split into multiple new plants. You simply need to leave a few pieces in the tank to maintain the population.

Sensitivity

low

It is relatively tough but sensitive to strong surface agitation. High water flow can push the plant underwater and cause it to rot. It also dislikes condensation dripping from tight aquarium lids.

Layout role

Floating

Its primary role is as a floating shade plant and nutrient exporter. It helps calm skittish fish by providing overhead cover and dimming bright lights. However, it can obscure lower plants if not carefully managed.