Brittle naiad (Najas minor) care guide

Group
Plants
Other names
Brittle naiad, Brittle waternymph, Najas fragilis, Caulinia minor
Family
Hydrocharitaceae (frogbit family)
Origin
Europe, North Africa and Asia, from the Netherlands and Morocco east to Japan and the Philippines; introduced and weedy in eastern North America
Water
freshwater
Maximum size
60 cm
Temperature
15–26°C
pH
6.5–8
Hardness
5–20 dGH
Care level
beginner
Lighting
Medium light; CO2 not needed
Flow
Calm water

Care

Brittle naiad is a small, much-branched annual water plant that grows fully submerged in still water such as ponds, lakes and reservoirs, down to about 4 m. It belongs to the frogbit family, alongside Egeria and Hydrilla. In the aquarium it behaves like guppy grass: a loose, bushy tangle of thin stems that can be planted or simply left floating in mid-water. It makes good cover for fry and shrimp and soaks up nutrients quickly. Expect to thin it out often. The narrow, strap-shaped leaves (around 4–5 cm) sit in opposite pairs and have teeth along the edge that you can see without a lens. Stems snap very easily, which is how it spreads. The sources give no aquarium water figures. Water figures are our estimate, not from the sources. It is a temperate to subtropical plant, so it suits unheated tanks and ponds at least as well as tropical tanks, and as an annual it may die back after flowering. Never release this plant or dispose of it in drains or waterways; it is invasive in some countries (it is listed as a noxious weed in parts of the eastern United States). Sources: Wikipedia (en.wikipedia.org/wiki/Najasminor); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.

Breeding

Spreads readily from broken stem pieces: any fragment left floating or pushed into the substrate grows on. It also sets small seeds along the stems.

Compatibility and tank mates

Soft and fine, so goldfish, large cichlids and other plant-eating fish will graze it. Ideal for shrimp, livebearers and fry tanks, where the tangle gives shelter. Suits unheated and temperate tanks as well as tropical ones.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

About Aquatic-Auctions

  • Aquatic-Auctions (aquatic-auctions.com) is a UK online marketplace for aquarium and pond livestock and equipment: tropical and marine fish, corals, shrimp, snails and other invertebrates, aquatic plants, tanks, filtration, lighting and food.
  • Items are sold by auction, buy it now or classified advert, by hobbyist and business sellers in the UK.
  • Buyers pay sellers directly; Aquatic-Auctions does not hold the money. Hobbyist sellers must offer PayPal and may also take cash on collection. Business sellers take PayPal (required) or cash on collection, and bank transfer only once they have a seller rating of 50 out of 100, a company and pet-selling licence checked by Aquatic-Auctions, a bank account in the company's name, and bank details approved by Aquatic-Auctions.
  • Buyers are told to pay by PayPal Goods & Services, never PayPal Friends and Family, gift cards or crypto.
  • Live fish and other vertebrates must be sent by specialist live-animal couriers (for example APC Overnight or DX Express), never by Royal Mail. Some invertebrates and plants may go by Royal Mail Special Delivery or 1st Class within its rules.
  • Banned and invasive species (for example those on the GB invasive species lists) cannot be listed, and sellers must meet the site’s animal welfare standards.
  • Members must be 16 or over to buy (16 and 17-year-olds with a parent or guardian’s agreement); sellers must be 18 or over.
  • Business sellers show their address, company details and pet-selling licence to buyers. Seller ratings run from 0 to 100: +1 for each positive feedback, −1 for each negative.
  • The site includes a free community species wiki with care guides (water parameters, tank size, diet, temperament, breeding).
  • Aquatic-Auctions is run by Etavonni Tech Limited trading as Aquatic-Auctions (company number 10204188), Aldershot, Hampshire, UK. Contact: info@aquatic-auctions.com.