Guppy Grass (Najas guadalupensis) - Bagged

Guppy Grass (Najas guadalupensis) is one of the fastest, most forgiving plants in the hobby and something close to a secret weapon for breeders. Its fine, needle-like leaves knit into a dense tangle that fry, shrimplets, and shy fish vanish into, while the plant strips nitrate and excess nutrients out of the water column quickly enough to starve out algae. No CO2, no substrate, and no special lighting required, you simply drop it in. Browse our full selection of freshwater aquarium plants.

Care Guide

• Lighting: Low to high. It grows under almost anything, and brighter light simply makes it denser and faster.
• CO2: Not required. This is a true low-tech plant, though it responds quickly to liquid fertilizer.
• Temperature: 68 to 82°F for tropical tanks, and it tolerates water down into the 50s, so it also works in unheated tubs and outdoor summer setups.
• Growth: Very fast. Plan on thinning it regularly, especially in a well-fed tank.
• Handling: The stems are brittle and snap easily. That is completely normal, and every broken fragment grows into a new plant.
• Water column feeder: It takes in nutrients through its leaves rather than roots, so dosing the water is what keeps it lush.

Specifications

Planting and Propagation

Guppy grass has no meaningful root system, so treat it as a floating or loosely anchored plant rather than something you bury in the substrate. Two easy options:

• Float it: The simplest approach and the most common. Let the portion drift at the surface, or tuck it into a back corner where the flow holds it in place. Floating gives you the thickest fry cover.
• Anchor it: Slide the base of a few strands under a rock or about an inch into the substrate. It will stay put, though it never grips like a true rooted stem plant.

Propagating it takes no effort at all. Break off a piece and it regrows into a full plant within a couple of weeks, which is why one bagged portion usually turns into more guppy grass than you planned on. Thin it before it shades out the plants underneath, and please never release trimmings into local ponds, creeks, or storm drains. Excess goes in the trash or the compost bin.

Why Breeders Keep It Around

• Fry survival: Thick enough that livebearer fry from guppies and endlers make it to adulthood in a community tank without a separate grow-out setup.
• Nitrate export: It pulls nutrients out of the water fast, which makes it a go-to fix for a heavily stocked tank or one that keeps fighting algae.
• Live food factory: The tangle harbors copepods, infusoria, and tiny snails, free first food for fry and a natural hunting ground for an Indian Pea Puffer.
• Shrimp habitat: Neocaridina shrimp graze biofilm off the leaves, and shrimplets use the same cover the fry do.

Pairs Well With

• Hornwort and Anacharis, the other two no-effort nitrate sponges
• Frogbit or Salvinia for shade above the tangle
• Seachem Flourish or Aquarium Co-Op Easy Potassium to feed the water column
• More freshwater aquarium plants

FAQ

Do I have to plant it?
No. Guppy grass is happiest floating and has no real roots, so planting it is optional. Most people just drop the portion in and let it drift.

Will it take over my tank?
It can if you let it, which is exactly why it works so well. Pull out a handful every week or two, and treat that as routine maintenance rather than a problem.

Why did it fall apart when I moved it?
The stems are naturally brittle and shed pieces whenever they are handled. Nothing is wrong. Every fragment that stays in the tank becomes a new plant.

Is it safe with shrimp, fry, and snails?
Completely. It is one of the best plants you can add to a shrimp tank or a breeding setup, and nothing in it will harm invertebrates.

Can I use it in an outdoor tub over the summer?
Yes. It handles cool water and full sun well and is a common choice for outdoor livebearer tubs. Bring it back inside before the first hard freeze, and never dump trimmings into natural water.