Detritus worms (Nais spp.) care guide

Group
Other invertebrates
Other names
Nais worms, Naidid worms, White detritus worms
Family
Naididae
Origin
Worldwide in fresh water; arrives with plants, gravel and fish
Water
freshwater

Care

Nais is a genus of tiny freshwater worms in the family Naididae, found worldwide. In the hobby, the thin, white to clear worms, a few millimetres to about 2 cm long, seen wriggling on the glass or in the gravel are often Nais or related worms, and are called detritus worms. Our sources have little on this species; the figures are general guidance, not from a source. How they arrive: with plants, gravel, decorations or the water fish are bagged in. They live in every mature tank in small numbers. Harmless or not: they are harmless, and helpful as they break down detritus and leftover food in the substrate. They do not harm fish, shrimp or plants. A sudden swarm on the glass usually means overfeeding, too much waste or low oxygen, so treat it as a warning: feed less, vacuum the gravel and do a water change. They should not be confused with planaria (flatworms with a triangular head), which can harm shrimp, or with hydra. Fish and shrimp eat them as a natural snack. They are not sold as livestock. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never dose them in a tank holding this animal, and check the label of any treatment or fertiliser before use. Sources: Wikipedia (en.wikipedia.org/wiki/Nais(annelid)). Checked October 2026.

Diet

Detritus, bacteria, algae and leftover food in the substrate and on surfaces.

Breeding

Nais worms reproduce mainly by splitting into new worms (budding or fission), which is why numbers can rise quickly when food is plentiful. Reduce feeding to bring numbers down.

Compatibility and tank mates

Harmless to fish, shrimp, snails and plants, and eaten by many fish. Large numbers indicate overfeeding rather than a direct threat.

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

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