Common Nase

About

The nase is a river-current specialist built around one tool: a straight, cross-cut mouth on the underside of the head whose lower lip carries a thick horny sheath. FishBase spells the etymology out — Chondrostoma is Greek for cartilage-mouth, and the name refers to the horny layer on the lower lip. The fish uses it like a chisel to shave algal film off stones, and the Lithuanian Red Data Book account says adults become narrow specialists that eat nothing but periphyton and detritus, all year round. Lithuanian Wikipedia calls it the only almost purely herbivorous native fish in Lithuania and notes something a stocking calculator should find interesting: European work has shown that by scraping the stones clean the nase improves spawning conditions for barbel, asp, grayling and other river fish, so rivers with nase hold more of them. It is not small. FishBase gives 50 cm and 1.5 kg with a common length of 25 cm and a maximum age of 15 years; Lithuanian Wikipedia records up to 56 cm, and English Wikipedia cites specimens up to 58.5 cm and 3.4 kg. It is gregarious, shoals along the bottom in moderate current, and migrates tens of kilometres upstream to spawn on shallow gravel. It is also a coldwater river fish that spawns at 6–12 °C. Nothing about that fits an aquarium, and everything about it fits a big, cold, fast, sunlit river.

Care

Read this before buying: in Lithuania the nase is a protected species. It has been in the Lithuanian Red Data Book since 1998 (category 2 (V), then 3 (R) from 2000, and CR under the IUCN categories used since 2019), it is on the country's protected species list, and the amateur fishing rules are explicit that Red Data Book species may not be taken at all, year-round, without exception. The Fisheries Service runs a restocking programme — 15,000 fish released into Lithuanian rivers in 2019, 23,000 in 2020 and 31,000 into the Šventoji in 2022, brought in from Poland. That is the context for a shop offering one. The EU picture is different again: seven other Chondrostoma species are named in Annex II of the Habitats Directive and this one is not, so the protection here is national, not European. English Wikipedia states that the nase is protected under the Bern Convention on the Conservation of European Wildlife and Natural Habitats; we have not read that instrument's appendices directly, so treat it as a pointer, and check your own country's rules — in parts of central Europe it is a legal sport fish. As an animal: this is a 50 cm shoaling rheophile. Five or more, a minimum of 5,000 litres and four metres of length, a stone and coarse-gravel bed, strong but not extreme flow — the Red Data Book account says the nase avoids both still water and too-strong current and holds in moderately fast stretches — near-saturated oxygen and cold water — 10–18 °C, never a heater. It cannot be fed like a normal fish: it grazes algal film off stone, so it needs a sunlit, algae-growing surface, with spirulina wafers and blanched greens as a poor substitute. It will not eat your plants — its whole diet is the film on the rocks, not the leaves — but nothing about this species belongs in a living-room tank.

Diet

Algae grazer: adults scrape periphyton and detritus off stones with a cartilaginous lower lip, year-round, with invertebrates taken mainly when algae are scarce. Needs sunlit, algae-growing stone; spirulina wafers and blanched greens are a substitute at best.

Telling males from females

What works for this species, most reliable first.

• Belly depthA hint only · only on well-fed adults, and only as a comparison

  For most tetras, barbs and rasboras this is all there is: a conditioned female is deeper through the belly than a male of the same length.

Also in these lists

Similar species

Same category and the closest water parameters — if this species isn't quite it, start here.

Sold in Lithuania

These Lithuanian shops listed this species in their public catalogue (checked August 8, 2026). Stock moves — ask before you travel.

These links are unpaid: we get nothing for them and ask for nothing.

Frequently asked questions

What tank size does a Common Nase need?

A Common Nase needs an aquarium of at least 5000 litres (1320.9 US gallons) with a footprint at least 400 cm (157.5 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Common Nase need?

Common Nase does best at 2–22 °C (35.6–71.6 °F), pH 6.5–8.5 and a general hardness of 8–20 °dGH.

What group size does a Common Nase need?

Common Nase is a social species — keep a group of at least 5 so natural behaviour emerges and stress stays low.

Is the Common Nase suitable for beginners?

Common Nase is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.

Sources

• FishBase — Chondrostoma nasus (Common nase)
• Lietuvos raudonoji knyga — Skersasnukis (Chondrostoma nasus)
• Vikipedija — Paprastasis skersasnukis
• Wikipedia — Common nase
• Council Directive 92/43/EEC (Habitats Directive), ANNEX II — as published by legislation.gov.uk
• Lietuvos raudonoji knyga — Lietuvos Respublikos saugomų gyvūnų, augalų ir grybų rūšių sąrašas 2020 m.
• Medžioklė ir žvejyba — Žvejybos taisyklės, leistini žuvų dydžiai (2026)