Amazon frogbit

Quick facts

Max height

3 cm

Growth rate

fast

Difficulty

beginner

Placement

floating

Propagation

runners

Water parameters

Temperature

18–30°C

pH

6.0 to 7.5

Hardness

0 to 20 dGH

Light and nutrients

Lighting

low

CO2

not needed

Substrate

floating

Feeding

feeds from the water column (use liquid fertilizer)

Substrate

What this plant roots into (or attaches to). The substrate affects both plant nutrition and water chemistry; see each linked page for full effects.

This plant feeds primarily from the water column, so substrate choice matters more for its fish-tank compatibility than for plant nutrition.

With fish

Plant-eating fish

will be eaten by mollies, silver dollars, large goldfish, and other plant-grazers

Diggers (corydoras, loaches)

fine - root system or attachment style handles it

Root-disturbing fish

tolerates fish that disturb roots

Habitat

Native to slow-moving and still freshwater across Central and South America: river oxbows, flooded forest pools, pond margins, and sheltered lake coves from Mexico through Brazil. The species (Limnobium laevigatum) is a floating plant with rosettes of round, spongy leaves (2–5 cm diameter) that sit flat on the water surface, with long trailing roots hanging into the water column below. The spongy leaf tissue contains air pockets (aerenchyma) that keep the plant buoyant. Under strong light and good nutrition, the leaves develop slightly cupped edges and a bright green color. Amazon frogbit reproduces rapidly by sending out stolons that produce daughter plants, forming dense floating mats. It has become invasive in parts of Australia, Japan, and Southeast Asia where introduced specimens escaped into local waterways.

Outdoor pond use

This species transitions to outdoor ponds well, not just indoor aquariums.

Outdoor pond zones (USDA)

8 to 13 (winter low around -12°C or warmer)

Below the minimum zone, the plant won't overwinter outdoors but can still be grown seasonally and overwintered indoors. Several pond-friendly species (water hyacinth, water lettuce, parrot's feather) are regulated as noxious in some jurisdictions; check the legality data on the profile before releasing anything to an outdoor body of water.

Care notes

Hard to kill. Amazon frogbit pulls nitrate and ammonia from the water column at a useful rate, which is why fishkeepers add it to overstocked or newly cycling tanks as a form of biological filtration. The trailing roots also serve as hiding spots for fry and shrimp. Growth is fast under moderate to strong lighting; a single plant can cover a small tank surface in 2-3 weeks. The main maintenance task is thinning: remove excess plants weekly to prevent the mat from blocking all light to submerged plants below. If it covers the surface completely, it will starve everything underneath of light. Condensation dripping from a closed lid can damage the leaves (they rot where water sits on the upper surface), so either leave a small gap in the lid or use a light that generates enough heat to evaporate condensation. Surface agitation from strong filter outflow pushes frogbit against tank walls and damages roots; baffle the outflow or create a calm zone with airline tubing stretched across the surface to corral the plants. Propagation is automatic: daughter plants form on stolons. Remove excess regularly. Nutrient requirements are low; it pulls what it needs from the water column. Liquid fertilizer benefits growth if the tank water is very lean.

Further reading

• How to cycle a fish tank
• Water chemistry for fishkeepers: pH, GH, KH, and what they mean