European Bitterling Care Guide
Rhodeus amarus is a small native European cyprinid that spawns inside living freshwater mussels and prefers cool tanks.
Overview
Rhodeus amarus, the European bitterling, is a small native European cyprinid. FishBase records a maximum size around 11 cm. It is best known for its unusual reproductive strategy, in which eggs are deposited inside living freshwater mussels.
Taxonomy
- Family: Cyprinidae
- Genus: Rhodeus
- Scientific name: Rhodeus amarus
Habitat
According to FishBase, the species occurs across central and eastern Europe and northern Asia Minor, in the basins of the North, southern Baltic, Black, Caspian and Aegean Seas. Wikipedia adds a range from the Rhone in France to the Neva in Russia. It is a benthopelagic fish of temperate waters that favours plant cover over sandy and muddy bottoms in shallow areas.
Tank requirements
- Minimum tank volume: 80 L
- Temperature: 4-22 °C (39-72 °F)
- pH: 7.0-8.0
- GH: 8-18 °dGH
- School size: 6 or more individuals
- Lifespan: 4-6 years
Diet
The species is omnivorous. FishBase reports it feeds mainly on plants and to a lesser degree on worms, crustaceans and insect larvae.
Compatibility
European bitterling is a peaceful shoaling fish best kept in groups of six or more with other cool-water native species. It should not be mixed with tropical fish, and a long-term setup ideally includes living freshwater mussels for natural behaviour.
Breeding
FishBase describes a specialised strategy: the female uses an ovipositor to deposit eggs within the valves of a living mussel, and the male sheds sperm into the mussel's inhalant current to fertilise them. Wikipedia notes the eggs remain protected inside the mussel for about a month before the larvae become active.
Conservation status
IUCN Red List: Least Concern (assessed 2022).