Guppy Grass (Najas guadalupensis) shares its species name with Anacharis Najas in some taxonomic treatments but is sold and kept as a distinct hobbyist variety — a fine, fast-growing stem plant with a noticeably softer, more open leaf arrangement that produces a less dense but more three-dimensionally voluminous shelter structure when used as a floating or midwater plant. Where Anacharis Najas has a slightly more structured, firmer stem habit, Guppy Grass produces more flexible, loosely arranged stems that collapse into a soft, open tangle when floating — a structure that shrimplets and fry navigate through easily and that provides genuine concealment rather than just proximity to cover. It earns its common name from its long history as the first plant breeders reach for when breeding livebearers — the soft floating tangles catch falling fry immediately and provide the first cover they need in the critical hours after birth. Fully safe with all Neocaridina, Caridina shrimp, and snails.
Not RequiredCO₂
64–82°FTemperature
Low–HighLighting
What to Expect
Growth & Behaviour
Soft, flexible stems with fine whorled leaves in an open arrangement — Guppy Grass stems are more pliable and less structured than Anacharis Najas — the fine, whorled needle leaves are arranged slightly less densely, giving each stem a softer, more open appearance at close range and a lighter, more airy mass quality when viewed as a floating bundle. The soft structure is what makes it particularly effective as a fry shelter — the open tangle allows small animals to move through it freely while remaining visually concealed.
Exceptional floating shelter for fry and shrimplets — as a floating plant or midwater tangle, Guppy Grass produces the best fry-scale shelter in the catalog — the combination of soft, pliable stems, open leaf arrangement, and the three-dimensional volume of a floating bundle creates a structure that newly born fry and shrimplets move into and remain within for hours and days after release. The plant does not trap or harm small animals — it provides refuge they actively seek out and remain in voluntarily.
Very fast growth rate under good light — like all Najas, Guppy Grass grows rapidly under medium to high light — adding several centimetres of new growth per day under ideal conditions and producing a substantial floating mass within weeks of introduction. The growth rate is the source of its primary functional value: rapid nutrient uptake from the water column that measurably reduces nitrate levels in breeding and shrimp tanks between water changes.
Plant or float — performs differently in each mode — planted in substrate Guppy Grass grows upright and can fill background and midground zones; floating freely or weighted at mid-depth it forms the soft open tangle that defines its shelter function. In breeding setups and shrimp tanks the floating mode is usually the primary goal — a loose bundle dropped into a tank immediately creates shelter without any preparation or waiting for roots to establish.
Propagates by fragmentation — trimmings grow independently — any section of stem trimmed from the main plant grows independently when returned to the water. Regular trimming is simultaneously regular propagation — a self-sustaining process that maintains the plant at the desired density while producing additional material for separate setups, sharing, or expanding shelter coverage in the same tank.
How to Set It Up
Getting Started
1Choose planted or floating mode — for planted use, strip the lowest 3cm of leaves and push stems 2cm into substrate. For floating or midwater shelter use, place loose bundles directly on the surface or weight loosely at mid-depth with a small stone. In breeding and shrimp tanks the floating mode requires no preparation — drop in a bundle and it immediately provides functional shelter.
2Use floating bundles for maximum fry and shrimplet survival — in any breeding setup — mesh breeders, breeding boxes, or the main tank during active shrimp breeding — floating bundles of Guppy Grass placed in the setup before fry or shrimplets are released provides immediate, ready-made cover. Maintain a small floating colony in the main tank and move portions to breeding setups as needed.
3Trim weekly to manage growth in display tanks — under good light Guppy Grass grows quickly enough to require weekly trimming in tanks where layout composition matters. Cut stems to the desired length and return trimmed sections to the float or replant — do not discard unless the population is already at the desired density. In breeding or shrimp-focused tanks where coverage is the goal, less frequent trimming and larger floating masses produce better shelter outcomes.
4Minimal fertilisation needed in stocked tanks — in a tank with regular shrimp feeding the ambient nutrient load is typically sufficient to fuel vigorous growth without additional liquid fertiliser. In lightly stocked or frequently water-changed tanks, a balanced liquid fertiliser dosed two to three times weekly supports steady growth.
💡 Bonus Tip
Keep a dedicated floating mass of Guppy Grass in one corner of the main tank at all times — not for display but as a permanent fry and shrimplet nursery resource. When a female shrimp becomes berried, move a portion of the floating mass to the breeding setup with her so the shrimplets are released directly into an established shelter environment rather than open water. The biofilm that develops on a long-established floating mass is substantially richer than fresh cuttings introduced at the moment of release.
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Browse more aquatic plantsPair Guppy Grass with Water Sprite, mosses, or floating plants for a complete breeding or shrimp setup. Browse our Aquatic Plants collection.
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