1 kinds · tap one for a closer look
Peaceful and shoaling; males guard mussels in spring.
This one is best kept on its own, or with its own kind.
Peaceful and shoaling; males guard mussels in spring.
Check your local laws. Listed (as Rhodeus sericeus amarus) in Annex II of the EU Habitats Directive 92/43/EEC, so EU states must designate conservation areas for it, and in Annex III of the Bern Convention. In Great Britain, where it is introduced, release is regulated under the Wildlife and Countryside Act 1981. The US Fish & Wildlife Service rates its invasion risk to the US as high (a screening, not a ban). Check the rules where you live before you buy one, and never release it into the wild.
Small pellets, flake and frozen foods.
Tap a food to see what it is.
In spring males take on bright nuptial colours and defend territories around mussels; females grow a long egg-laying tube (ovipositor).
Common problems. Tap one to see the signs. This is a guide, not a diagnosis.
Mussel spawner ·
The female uses her ovipositor to lay eggs onto the gills of a live freshwater mussel (Unio or Anodonta) through its exhalant siphon; the male sheds sperm at the inhalant siphon. A tank or pond with live mussels is needed.
Group with live mussels.
Large cool tank with live freshwater mussels and plants.
Spring warm-up.
One to six eggs per laying, about 80-300 per female per season. Eggs hatch in 24-36 hours, and the young stay in the mussel for 3-4 weeks before swimming out at about 10 mm.
Fry leave the mussel after about 4 weeks and feed on infusoria.
A small European fish famous for laying its eggs inside living freshwater mussels; it cannot breed without a mussel host. It was once used in human pregnancy tests.
Marcus Bloch described this fish in 1782 as Cyprinus amarus. It is famous for its breeding behaviour: females lay eggs inside freshwater mussels using a long ovipositor. The young develop inside the mussel before swimming out.
First described by Marcus Elieser Bloch in 1782. Named for 'amarus' means 'bitter'.
12 facts checked with sources
Older literature (and the EU Habitats Directive annex) calls it Rhodeus sericeus amarus; R. sericeus is now the Amur bitterling of East Asia. Shops may also sell the East Asian rosy bitterling R. ocellatus as "bitterling". Coldwater fish.
Eschmeyer's Catalog of Fishes: Rhodeus amarus (online version updated 21 Sep. 2026) · FishBase: Rhodeus amarus summary (main ref. Kottelat & Freyhof 2007)Legacy has no family; value is new. Formerly a subfamily of Cyprinidae.
FishBase: Rhodeus amarus summary (main ref. Kottelat & Freyhof 2007)size-pick: TL. Common length 5 cm, maximum record 11.2 cm. Legacy 8 cm is a large adult; no Seriously Fish profile.
FishBase: Rhodeus amarus summary (main ref. Kottelat & Freyhof 2007) · Wikipedia: European bitterling (cites FishBase; Tarkan et al. 2005)No keeping range found. A temperate fish that spawns from about 10-15 °C up, optimum 23 °C; legacy top of 22 °C is plausible.
US Fish & Wildlife Service: Ecological Risk Screening Summary, European Bitterling (Rhodeus amarus) · Croatian Agency for Environment and Nature (HAOP): Monitoring programme for Rhodeus amarus (government PDF)Most wild fish live 1-2 years (mature at 1 year); 5 years is exceptional. Captive lifespan not sourced. Legacy 4-5 years is the top end.
FishBase: Rhodeus amarus summary (main ref. Kottelat & Freyhof 2007)Benthopelagic; no source says mid-water in substance.
FishBase: Rhodeus amarus summary (main ref. Kottelat & Freyhof 2007)Legacy has no range; value is new. Introduced to Britain and Italy.
FishBase: Rhodeus amarus summary (main ref. Kottelat & Freyhof 2007)Legacy also mentions male tubercles; not checked.
US Fish & Wildlife Service: Ecological Risk Screening Summary, European Bitterling (Rhodeus amarus)Spawns late April to August.
US Fish & Wildlife Service: Ecological Risk Screening Summary, European Bitterling (Rhodeus amarus) · Croatian Agency for Environment and Nature (HAOP): Monitoring programme for Rhodeus amarus (government PDF)Legacy "few eggs per female" understates the seasonal total; legacy 4 weeks in the mussel is right.
Croatian Agency for Environment and Nature (HAOP): Monitoring programme for Rhodeus amarus (government PDF) · Wikipedia: European bitterling (cites FishBase; Tarkan et al. 2005)Annex II means habitat protection, not a keeping ban; check national rules before collecting wild fish. The host mussels (Unio, Anodonta) are protected in some countries, but no source was checked for that.
Croatian Agency for Environment and Nature (HAOP): Monitoring programme for Rhodeus amarus (government PDF) · US Fish & Wildlife Service: Ecological Risk Screening Summary, European Bitterling (Rhodeus amarus)