Amazon frogbit

Limnobium laevigatum

Also known as Frogbit, South American spongeplant, Smooth frogbit

FreshwaterFloatingRunnersPlantletsSide shoots

Invasive. Can be invasive in warm climates and is regulated in some areas. Never release into the wild; dispose of in the trash.

Amazon frogbit (Limnobium laevigatum) — Cardex · Public domain

Care at a glance

Light: Medium light
CO2: No CO₂ needed
Growth rate: Fast
Placement: Floating
Type: Floating
Temperature: 68–82°F (20–28°C)
pH: 6.0–7.5
Hardness: 2–15 dGH
Max height: 2 in (5 cm)
Spread: 5.9 in (15 cm)
Nutrient uptake: Water column
Growth region: Submersed or emersed
Difficulty: Beginner
Origin: Central and South America
Family: Hydrocharitaceae

Overview

Set it on the surface and it grows quickly under ordinary aquarium light with no CO2 or substrate, its long roots acting as a strong nitrate filter and a refuge for shrimp and fry. It multiplies fast and will blanket the surface if left alone, so thin it regularly to keep light reaching plants below. The usual complaints are melting or yellowing leaves from condensation and hard surface spray hitting the crown, and stunted pale growth from a lid trapping heat or from a nutrient deficiency, so leave an air gap, keep surface flow gentle and dose a complete liquid fertilizer.

In the wild

Amazon frogbit is a free-floating plant native to Central and South America, including the Amazon basin, where it drifts across still and slow-moving ponds, lakes, marshes and river backwaters. It floats with rounded glossy leaves on the surface and a thick mass of long roots trailing below into the water. In bright open conditions older plants can lift their leaves up off the surface into a low emersed rosette.

Good to know

Limnobium laevigatum belongs to the family Hydrocharitaceae, the same family as Vallisneria and Egeria. The undersides of its floating leaves carry a spongy, air-filled aerenchyma tissue that gives it buoyancy, which is the origin of the alternate name spongeplant. It spreads aggressively by stolons that bud off daughter plants, forming dense connected colonies, and can also flower and set seed.

Did you know

Frogbit is so productive at sucking up nutrients that it is used in wastewater treatment and as a green manure, and that same vigor has made it an invasive nuisance in warm regions, so it should never be released outdoors.