Limnobium spongia Care Guide
American frogbit, a floating plant with spongy-undersided leaves that provides surface shade and nutrient uptake in soft, slow-moving water tanks.
Compiled by Aquairi from published sources · Published · Updated
Overview
Limnobium spongia, the American frogbit, is a floating plant in the family Hydrocharitaceae. It produces heart-shaped to nearly rounded floating or emersed leaves, roughly 2-7 cm in diameter, with a thick layer of spongy aerenchyma on the underside of floating leaves that aids buoyancy. It provides effective surface coverage and shade. Following taxonomic revision the species is also classified as Hydrocharis spongia.
Taxonomy
- Family: Hydrocharitaceae
- Genus: Limnobium (also treated as Hydrocharis following revision)
- Scientific name: Limnobium spongia
- Common name: American Frogbit
Habitat
The species is native to the central and southeastern United States, ranging across states from Texas and Florida north to New York and Connecticut. It thrives in slow-moving or stagnant water with muddy substrate, including sloughs, ditches and swampy forests. Its whitish root systems hang in the water column and can host zooplankton.
Tank requirements
- Light: medium
- CO2: not required
- Temperature: 18-28 °C (64-82 °F)
- pH: 5.5-7.5
- GH: 2-14 °dGH
- Placement: floating
- Growth rate: fast
Care and growth
As a fast-growing floating plant it shades the water below, which can suit blackwater and biotope setups, and it draws nutrients from the water. Keep humidity above the tank moderate, since condensation or droplets sitting on the leaves of floating plants can cause melt. Thin the mat periodically so light still reaches plants beneath.
Propagation
The plant spreads readily by runners (stolons) and division. New rosettes form on runners and can be separated once they have their own roots and leaves.
Propagating Limnobium spongia (American Frogbit) by Runners and Division
Overview
Limnobium spongia, American frogbit, is a floating aquatic plant with heart-shaped or nearly rounded leaves 2-7 cm across. Floating leaves carry a thick layer of spongy aerenchyma on their underside, while emersed leaves lack this spongy tissue. With long trailing roots it provides excellent surface shade and cover, making it popular for blackwater and biotope tanks.
In its native southeastern United States it grows in sloughs, ditches and swampy forests in slow-moving or stagnant water, so it thrives in calm, still surfaces.
Propagation Method: Offsets on Runners
American frogbit propagates by sending out runners, spreading like a connected web of plants. Daughter plants form naturally along these runners without any manual intervention, so the colony multiplies on its own. To deliberately propagate, you simply separate established daughter rosettes, a form of division.
Step-by-Step
- Let the parent plant grow until it sends out runners with small daughter rosettes attached.
- Wait until each daughter has its own leaves and a few roots of its own.
- Gently pinch or snap the runner to separate the daughter from the parent.
- Float the separated plant back on the surface in a calmer area so it can settle.
- Remove whole connected clumps in one piece when thinning, as the web lifts out easily.
Conditions for Healthy Growth
- Placement: free-floating on a calm, still surface.
- Temperature: 18-28 C.
- pH 5.5-7.5, GH 2-14.
- Lighting: medium light; floating plants grow very quickly and absorb nitrogen from the water.
- Avoid strong surface agitation, which wets and rots the floating leaves.
Maintenance
Thin the colony regularly, roughly every couple of weeks, by scooping out connected clumps. Do not let it cover the entire surface, or it will out-shade the plants below and reduce dissolved oxygen in the water.
Common Challenges
Inside the tank the main issue is the opposite of weakness: overgrowth. Frequent thinning keeps light reaching plants below and prevents oxygen depletion under a closed surface mat.