Black RanchuBlack Ranchu (Carassius auratus) is the most revered of all fancy goldfish varieties — known as the 'King of Goldfish' in Japan, where Ranchu breeding has been elevated to a fine art over centuries. The Ranchu is distinguished by its absence of a dorsal fin — the back is a smooth, deeply arched curve from head to tail with no fin — combined with a very deep, short body, a pronounced head growth (wen) similar to the Oranda, and tucked-under tail fins. This fish displaying deep black coloration across the entire body. Black Ranchu are particularly unusual and sought-after — the all-black color on the distinctive Ranchu profile is striking. Note that black coloration in goldfish can fade over time.Feeding & Care Tip: Hikari Fancy Goldfish slow-sinking pellets are the ideal staple for fancy goldfish — the slow sink rate gives these slower-swimming varieties time to feed without gulping air at the surface, which can cause swim bladder problems. Sera Goldy Color Spirulina enhances red and orange coloration. Supplement 2–3× per week with Hikari Frozen or Freeze-Dried Baby Brine Shrimp or Hikari Frozen Daphnia. If keeping alongside slim-bodied goldfish, offer Hikari Goldfish floating pellets at the same time — the slim-bodied fish will take the floating food while the fancies feed at their preferred mid-water level, ensuring both types eat well.The Ranchu was developed in Japan from Chinese lionhead goldfish over centuries of meticulous selective breeding. Traditional Japanese Ranchu shows are judged on the balance between head growth, body depth, back arch, and tail angle — criteria refined over generations. The absence of the dorsal fin and the deeply rounded body make the Ranchu one of the slowest-swimming fancy goldfish.Keep in groups of two or more with other slow-swimming fancy varieties. The Ranchu's dorsal-less body and short, deep shape make it one of the more delicate fancy goldfish — more susceptible to swim bladder issues and poor water quality than hardier varieties like the Fantail. Feed only slow-sinking or bottom foods — surface feeding causes air gulping which worsens buoyancy problems. Fancy goldfish require a larger aquarium than most people expect — a minimum of 20 gallons for a single fish, with an additional 10 gallons per additional fish. A long, wide tank is preferable to a tall, narrow one — fancy goldfish spend most of their time in the lower half of the water column and benefit more from bottom area than height. Gentle filtration that moves the water without creating strong currents is ideal — the egg-shaped body of fancy goldfish makes them poor swimmers in turbulent water.Goldfish are among the longest-lived aquarium fish — well-kept fancy goldfish regularly reach 10–15 years with excellent care. The investment in appropriate tank size, good filtration, and regular water changes is rewarded with a fish that becomes a genuine long-term companion. Filtration & Water Quality: Goldfish are high-waste fish that require robust filtration — significantly more than most tropical fish of equivalent size. A filter rated for at least twice the tank volume is recommended. Regular partial water changes of 25–30% weekly are essential. Despite their reputation as 'easy' fish, goldfish kept in under-filtered or overcrowded conditions decline quickly. Good filtration is the single most important factor in keeping goldfish healthy and long-lived.Care & Ideal Parameters Difficulty Moderate — Advanced Temperament Peaceful — keep with other slow fancy goldfish Typical Adult Size 6 inches (15 cm) Min. Group Size 2 minimum — 20 gallons per fish Ideal Temp 50–75°F (10–24°C) Ideal pH 6.5–8.0 Ideal GH 5–20 dGH Ideal KH 3–12 dKH Staple Food Hikari Fancy Goldfish (slow-sinking pellets); Sera Goldy Color Spirulina Treat / Supplement Hikari Frozen or Freeze-Dried Baby Brine Shrimp; Hikari Frozen Daphnia Origin China (captive-bred — all goldfish are domesticated Carassius auratus) Notes All-black Ranchu — unusual and sought-after. Black may fade with age or in warm/bright conditions. No dorsal fin. More delicate — advanced keeper.
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