Rosy Bitterling (Rhodeus ocellatus) Care Guide
Rhodeus ocellatus is an East Asian bitterling that lays its eggs inside living freshwater mussels.
Compiled by Aquairi from published sources · Published · Updated
Overview
The rosy bitterling, Rhodeus ocellatus, is a small temperate cyprinoid fish of the family Acheilognathidae from East Asia. Spawning males develop rosy flanks. The species is notable for a reproductive strategy that depends on living freshwater mussels.
Taxonomy
- Family: Acheilognathidae
- Genus: Rhodeus
- Scientific name: Rhodeus ocellatus
Habitat
According to FishBase the species occurs in eastern Asia and Taiwan as well as Russia. Wikipedia records it from the Amur River basin to the Pearl River basin, inhabiting ponds and reservoirs where freshwater mussels are abundant. It has been introduced beyond its native range, with documented adverse ecological effects, including in Japan.
Tank requirements
- Minimum tank volume: 80 L
- Temperature: 10-26 °C (50-79 °F)
- pH: 6.5-8.0
- GH: 8-18 °dGH
- School size: 6 or more individuals
- Lifespan: 4-6 years
Diet
Rhodeus ocellatus is an omnivore with a low trophic level. In aquaria it accepts prepared, live and frozen foods, fed about twice daily.
Compatibility
This is a peaceful, mid-water schooling species. It is best kept with other cool-water cyprinids and should not be combined with tropical fish that require consistently warm water.
Breeding
The female develops a long ovipositor about the length of her body and deposits eggs onto the gills of a living freshwater mussel, where the male's milt fertilises them. Wikipedia reports that two or three eggs are placed at a time, the process is repeated about ten times per season at 6-9 day intervals, and the young develop inside the mussel for roughly 15 to 30 days after fertilisation. A suitable mussel host is therefore required for reproduction.
Conservation status
The IUCN Red List assesses Rhodeus ocellatus as Data Deficient (assessed 4 September 2010).
Breeding Rosy Bitterling
Overview
The Rosy Bitterling (Rhodeus ocellatus) is an East Asian bitterling occurring from the Amur River basin to the Pearl River basin. Like other bitterlings it has a highly specialised reproductive strategy that depends on living freshwater mussels, with males turning rosy in the breeding season.
Sexing
Females develop a unique pipe-like ovipositor roughly as long as their body during breeding. Males change to a reddish, sometimes purple, colour during the spawning season to attract females, making the sexes easy to tell apart when in condition.
Breeding Setup
House a living freshwater mussel in the tank as the obligatory spawning site. The active spawning period runs from March to September, so a cool seasonal temperature regime supports breeding condition in this temperate-to-subtropical species.
Spawning Behavior & Trigger
The female uses her ovipositor to place eggs on the gill of the mussel, usually two or three eggs at once, and the male fertilises them by spawning into the mussel's gill cavity immediately afterwards. A female normally lays repeatedly at six- to nine-day intervals, about ten times in a season.
Egg & Fry Care
Eggs hatch after about three days, when the juveniles are about 2.8 mm long, and they develop within the mussel's gills for roughly 15 to 30 days. The juveniles then swim out from the margin of the mussel's excurrent siphon at around 7.5 mm.