Duckweed (Lemna minor) is the smallest and fastest-growing floating plant in the catalog — tiny, bright green, oval fronds 2–4mm across that float individually or in small clusters at the water surface and multiply by simple division at a rate that no other floating plant approaches. Where Frogbit and Water Lettuce produce structured rosettes that spread steadily, and Salvinia produces clustered fronds that expand across the surface, Duckweed produces individual fronds that each divide independently into two, then four, then eight — doubling the colony size with each division cycle and covering available surface area within days under good light. The functional benefits are proportional to this growth rate: nitrate absorption more aggressive than any other floating plant in the catalog, a surface canopy dense enough to create genuine subdued lighting for shrimp and fry, and biofilm development across millions of tiny frond surfaces. Honest note: once introduced, Duckweed is essentially permanent in any tank with an open surface — small fragments transfer between tanks, adhere to equipment, and resist removal. Introduce knowing this. Fully safe with all Neocaridina, Caridina, and snails.
Not RequiredCO₂
50–86°FTemperature
Low–HighLighting
What to Expect
Growth, Function & Management
Fastest-growing floating plant in the catalog — colony doubles within days — individual fronds divide at a rate determined by light and nutrient availability. Under medium to high light in a nutrient-loaded tank, visible doubling of colony density can occur within one to two days. This growth rate means an introduced pinch of Duckweed becomes a complete surface covering within one to two weeks in most tanks — useful if rapid surface coverage is the goal, and the primary management challenge if not.
Most aggressive nitrate absorber in the catalog — measurable water quality impact — the biomass production rate of Duckweed under good light translates directly to nitrate uptake that measurably and rapidly reduces nitrate levels in shrimp tanks between water changes. In heavily stocked or less frequently water-changed tanks, a healthy Duckweed colony can absorb the equivalent of a partial water change worth of nitrates per week. The removed nitrates leave the system permanently when Duckweed is harvested and discarded.
Complete surface canopy — most thorough dappled light coverage available — a full Duckweed surface covering reduces light penetration to the tank by 30–70% depending on density, creating the most thorough dappled light and shade effect of any floating plant — each frond casts a tiny shadow and lets light through between fronds, producing a fine-grained, natural-looking dappled pattern at the substrate level. For shrimp that are more active and confident under cover, a Duckweed canopy produces the most uniformly shaded tank environment.
Essentially permanent once introduced — transfer prevention is impractical — Duckweed fronds are small enough to adhere to nets, siphons, hands, and plant leaves being transferred between tanks. Once a tank has Duckweed, preventing it from reaching other tanks requires dedicated equipment and careful management. Introduce with the understanding that you are making a long-term commitment to managing Duckweed in that tank. Do not introduce to a tank where you want to maintain a Duckweed-free surface.
Management is mechanical — harvest regularly to prevent complete surface cover — control colony density by physically removing excess fronds during water changes. Use a fine net, cup, or colander to skim the surface and remove the desired percentage of the colony. Discard removed Duckweed in compost or the bin rather than into any outdoor waterway — Duckweed is invasive in many regions when introduced to natural water bodies. Target 50–70% surface coverage as a maintenance goal — dense enough for benefits but not so dense that plant growth below is severely impacted.
How to Set It Up
Getting Started
1Introduce a small starter amount and allow it to establish — a tablespoon of Duckweed fronds is sufficient to establish a colony that will cover a standard nano tank surface within one to two weeks under good light. Introducing a small amount and allowing the colony to grow naturally is preferable to introducing a large amount immediately — the smaller introduction gives you more time to observe and calibrate management before coverage becomes dense.
2Reduce surface agitation in the Duckweed zone — direct filter outlet flow below the surface to minimise surface disturbance. Duckweed fronds that are repeatedly submerged by strong surface agitation decline and die — calm surface conditions allow the colony to spread and divide at maximum rate. In tanks with unavoidable surface agitation, use a floating plant ring to corral Duckweed in the calmest surface zone.
3Manage density by harvesting regularly — target 50–70% coverage — decide on a target surface coverage and harvest excess fronds weekly during water changes to maintain it. At 50–70% coverage the canopy provides significant shade and nutrient absorption benefits while allowing adequate light penetration for plants below. At 100% coverage, light to submersed plants is severely reduced and surface gas exchange is impeded.
4Use a dedicated net or cup for Duckweed management — designate one small net or cup exclusively for Duckweed management and do not use it in Duckweed-free tanks. This is the single most effective practice for preventing Duckweed transfer to tanks where it is not wanted.
💡 Bonus Tip
Duckweed is the most effective natural breeding-tank setup plant available — a breeding box or grow-out tank seeded with a dense Duckweed covering before fry or shrimplets are introduced provides immediate dappled light, continuous biofilm on millions of frond surfaces that tiny animals graze from day one, a visual cover layer that reduces stress in newly released young, and aggressive nitrate absorption that compensates for the elevated organic load of a densely populated breeding setup. The combination of functions that Duckweed provides simultaneously — cover, biofilm, nitrate control, and shade — in a single freely available plant makes it the best-value breeding setup addition in the catalog.
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Browse more aquatic plantsPair Duckweed with Guppy Grass, Water Sprite, or floating plant rings for a complete breeding or shrimp setup. Browse our Aquatic Plants collection.
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