Furry Diary

Not furry, but we like them anyway.

Rosy Bitterling

Rhodeus ocellatus

Also called Rhodeus ocellatus ocellatus (nominate subspecies)

SpeciesShort profile

From Eastern Asia, from the Amur River basin south to the Pearl River basin, including Taiwan and parts of Russia12

At a glance the quick version

Length4 to 9.2 cm21
Sizesmall
Males show striking rosy and purple breeding colours
Small and suited to cool, unheated water
Fascinating breeding partnership with freshwater mussels
21

Looks how to spot one

Small, deep-bodied, laterally flattened carp relative

A compact, flat-sided little fish with a bright silvery sheen. In the breeding months males take on rosy red to purple tones, which is where the name comes from, and females grow a thin egg-laying tube.21

Colourssilvery (both sexes)rosy red to purple flush (breeding males)2

Personality what they are like

A small, schooling fish of quiet, weedy water. Males become showy and attentive during the spring and summer breeding season.21

Grooming and care the hands-on bits

To see natural breeding the setup needs living freshwater mussels, as the female places her eggs inside them.21

Home where they are happiest

A temperate fish of shallow ponds, marshes and slow canals. FishBase gives a water temperature of about 18-24 C, pH up to 7.0 and hardness of 10-15 dH.1

Food basics what goes in the bowl

An omnivore that picks at small food items and plant or detritus matter.1

The story where it all began

The rosy bitterling is native to the river systems of East Asia. It reached Japan by accident in 1942, mixed in with shipments of grass carp and silver carp from mainland China, and has spread widely there since.2

Fun facts for the dinner table

  1. 1

    Females lay their eggs inside living freshwater mussels, and the young stay inside the mussel until they can swim.1

  2. 2

    A female may spawn around ten times in one season, roughly every six to nine days, laying just two or three eggs each time.2

  3. 3

    Hatchlings measure only about 2.8 mm and leave the mussel at about 7.5 mm long.2

  4. 4

    Young rosy bitterlings have a body shape compared to the bud of a matsutake mushroom.2

Recognised by the official bits

IUCN Red List
Data Deficient (assessed 4 September 2010)1
FishBase
Listed as used in the commercial aquarium trade1
Taxonomy
Two subspecies recognised: R. o. ocellatus and R. o. smithii2

The care rhythm Furry Diary remembers it for you

A typical home-care rhythm for a Rosy Bitterling. It is our own starting plan, not a vet's advice, and you can change every line in the app.

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Where this comes from

Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.

  1. FishBase: Rhodeus ocellatus fishbase.seused for size, distribution, water parameters, reproduction, IUCN status, trade use
  2. Wikipedia: Rosy bitterling en.wikipedia.orgused for size, colours, reproduction, history, subspecies, fun facts

Checked 2026-09-30. Text is written in our own words from these sources.