The Amazon Frogbit Care Guide: Stopping the Melt and Keeping the Roots

Limnobium laevigatum is the floating plant most people want and the one most people kill in the first fortnight. It is not difficult. It has one hard requirement that nothing else on your plant list shares, and almost every failure traces back to it.

Its leaves must stay dry

This is the whole guide in one line. Amazon Frogbit floats with its leaf surfaces above the waterline, and those surfaces are not adapted to being wet. Water sitting on top of a leaf causes it to yellow, soften and rot, and the rot spreads through the plant.

Three things wet the leaves:

• Surface agitation. A spray bar aimed across the surface, a strong HOB return, or an air stone under the frogbit will splash the leaves constantly. Aim outflow along the glass or below the surface, or fence the frogbit off from the turbulence.
• Condensation from a tight lid. A closed glass lid drips straight back onto the leaves. Leave an air gap, or run the tank open-topped.
• Your own hands. Push the frogbit aside when you work in the tank rather than submerging it, and shake off any leaf you do wet.

If your frogbit is melting and everything else in the tank is fine, this is why. It is not water parameters.

The roots are the reason to buy it

Frogbit sends down long, fine, trailing roots — often four to six inches, sometimes more. That root curtain is the point of the plant. It is where shrimplets and fry hide, where biofilm develops, and where a large amount of nitrate uptake happens.

Resist the urge to trim them for looks. Cutting the roots removes most of the plant's filtration value and the plant reinvests energy in regrowing them rather than making new leaves.

Root length is also a useful diagnostic. Very long roots usually mean the plant is searching for nutrients in a lean tank. Short, stubby roots mean the water column is rich.

Yellow leaves are almost always nutrients

Frogbit feeds entirely from the water column and it is a heavy feeder. In a lightly stocked or heavily filtered tank it runs out of nitrogen and iron and pales from the older leaves inward.

A general-purpose liquid fertiliser dosed to the tank is normally enough. If leaves are yellowing between green veins, that pattern points at iron specifically.

The distinction worth learning: rot starts at the leaf surface and is wet and brown; deficiency starts at the leaf edge or between veins and is dry and yellow. They have completely different fixes.

It will take over, and that is manageable

Under good conditions frogbit throws daughter plants on short runners and can double its coverage in a week or two. Left alone it forms a mat that blocks light to everything below it.

Thin it weekly by hand — scoop out a third and discard or share it. Do not let it reach full coverage before acting, because the plants underneath a closed mat are the ones that suffer, and stem plants stretch and go bare at the base.

Reduced light also reaches the frogbit itself. A crowded mat produces smaller leaves and a plant that looks stunted is often just competing with itself.

Frogbit, Dwarf Water Lettuce or Salvinia?

All three are commonly confused at a glance.

• Amazon Frogbit — round to heart-shaped glossy leaves, roughly half an inch to over an inch across, with a spongy tissue underneath. Long trailing roots.
• Dwarf Water Lettuce — ribbed, upright, velvety rosettes. Larger, and it grows upward as well as outward.
• Salvinia — small paired oval leaves covered in water-repellent hairs. Much smaller and far more tolerant of surface splash.

If your setup has surface movement you cannot change, Salvinia is the realistic choice. It shrugs off water on its leaves in a way frogbit will not.

A note on state restrictions

Floating plants that reproduce this quickly are regulated in a number of U.S. states. Check your local rules before ordering, and never release aquarium plants into natural waterways — dispose of trimmings in the bin or compost, not down a drain.

Quick reference

• Light — Low to medium
• CO2 — Not required
• Water — 68–82°F, pH 6.5–7.5
• Feeding — Water column feeder; liquid fertiliser needed in lean tanks
• Placement — Floating
• Propagation — Daughter plants on runners
• Difficulty — Beginner

Shop Amazon Frogbit · Shop Tiger Stripe Frogbit