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American Frogbit
Limnobium spongia
Also known as American Spongeplant, Frogbit
Plantae›Tracheophyta›Magnoliopsida›Alismatales›Hydrocharitaceae
📍 South America
A hardy floating plant with rounded, kidney-shaped leaves and a spongy underside — the North American cousin of Amazon Frogbit. Its trailing roots give shrimp and fry cover and pull nitrate straight from the water column, while the leaves shade the tank and curb algae. Undemanding: no CO₂ or root tabs — just keep the leaf tops dry (aim surface flow away from it) and give it light.
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Compatible Livestock
Shrimp hide in dangling roots and benefit from the plant's shade; frogbit provides grazing surfaces for biofilm
Small, peaceful fish that shelter under frogbit canopy without damaging delicate leaves
Algae-eating fish that won't uproot or consume frogbit; benefits from shade provided by plant
Peaceful livebearers that appreciate surface cover; fry find excellent refuge in root system
Excellent companion plant that creates layered cover and shares similar low-nutrient tolerance
Foreground plant that complements frogbit's surface coverage; both thrive in moderate to high light
Common Diseases
Nutrient Deficiency
Yellowing leaves, stunted growth, pale coloration, leaf holes or necrosis
Dose liquid all-in-one fertilizer weekly; ensure adequate lighting to support photosynthesis; test water parameters and adjust macronutrients (nitrogen, phosphorus, potassium) as needed
Algae Overgrowth on Leaves
Green or brown algae coating leaf surfaces, reduced light penetration, slowed growth
Increase water circulation, reduce photoperiod to 8-10 hours daily, manually remove affected leaves, introduce algae-eating fish like Otocinclus or add liquid algaecide if severe
Root Rot
Darkening or mushy roots, foul odor, leaf yellowing and wilting, plant sinking
Improve water circulation and aeration; perform partial water changes; remove severely affected plantlets; ensure roots are not buried in substrate; reduce organic buildup with regular maintenance
Iron Deficiency Chlorosis
Yellowing of new leaves while veins remain green, stunted growth, pale appearance
Dose liquid iron supplement (chelated iron) 1-2 times weekly; increase overall fertilization; ensure adequate lighting to support nutrient uptake
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Quick Facts
- co2
- Not required
- diet
- Nutrient absorption from water column
- light
- Medium to high
- tank size
- No minimum – floating
- growth rate
- Fast
Water it likes
- ph
- 6.0–7.5
- ammonia
- 0 ppm
- nitrate
- <40 ppm
- hardness
- 1–15 dGH
- temperature
- 64–82°F (18–28°C)
Legality
No state or federal restrictions on record for this species.
Not legal advice, and possibly incomplete or out of date. Rules vary by state and locality and change over time — always confirm the current regulations with your state wildlife or agriculture agency before buying, keeping, or shipping this species.