Ranchu

Ranchu goldfish have round, hunched bodies and lack a dorsal fin. Their tail peduncle points downward, making it difficult to swim for long periods, so smaller tanks around 20-30 gallons are appropriate for these fish. Your Ranchu may or may not have a partial wen on the head, cheeks, or operculum (gill cover). A lack of dorsal fin makes it even harder to swim thus a strong flow in the aquarium must be avoided.