The Ranchu Goldfish is a cherished member of the fancy goldfish family, celebrated for its distinctive appearance and calm temperament. Here’s a detailed care guide based on the provided information:

Species Overview

• Common Name: Ranchu Goldfish
• Origin: Japan (17th century, later introduced to China).
• Lifespan: 8–15 years (longer with optimal care).
• Size: Typically 5–8 inches; up to 12–18 inches in larger tanks or ponds.

Appearance

• Body Shape: Egg-like, with a smooth curve on the back and no dorsal fin.
• Fins: Double-fan tail with a tucked base, contributing to a hunchbacked profile.
• Head Growth: “Helmet” or wen covers the head, gills, and cheeks. Its size and prominence vary among individuals.
• Colors: Gold, white, black, and calico.

Tank Requirements

• Minimum Tank Size:
  • 30 gallons for a single adult (juveniles can start in 10 gallons).
  • 55 gallons or more is preferable, especially for multiple fish.
  • Add 5 gallons for each additional fish.
• Preferred Setup:
  • Soft substrate like sand or smooth pebbles to accommodate digging behavior.
  • Hardy plants (e.g., anubias, java fern) anchored to rocks to avoid uprooting.
  • Decorations without sharp edges to prevent injury.
• Filtration & Aeration:
  • Use a robust filtration system to handle high waste output.
  • Avoid strong currents; opt for air stones for gentle oxygenation.
• Lighting: Moderate, replicating natural pond-like conditions.

Water Conditions

• Temperature: 65–75°F (cooler range).
• pH: 7.0–8.0 (neutral preferred).
• Hardness: 5–19 dH.
• Maintenance: Weekly water changes to maintain stability and low ammonia levels.

Diet

• Type: Omnivorous.
• Staple: High-quality goldfish flakes or pellets designed to enhance color and nutrition.
• Supplements:
  • Protein: Bloodworms, tubifex, and freeze-dried shrimp.
  • Vegetables: Blanched spinach, zucchini, or peas.
• Feeding Schedule: 2–3 times daily; only provide what can be consumed in 2 minutes to prevent overfeeding.

Behavior and Temperament

• Swimming Style: Slow-moving, with a graceful “bobbing” motion.
• Activity: Exploratory but calm; enjoys foraging in the substrate.
• Aggression: None. Suitable for peaceful community tanks.
• Tank Mates:
  • Ideal: Other fancy goldfish (e.g., Lionhead, Black Moor, Pearlscale), guppies, zebra danios, dojo loaches, or platies.
  • Avoid: Aggressive or fin-nipping species like cichlids or tiger barbs.

Breeding

• Sexing: Males develop white tubercles on gill plates during maturity.
• Spawning:
  • Use a breeding tank with fine-leaf plants or spawning nets to catch eggs.
  • Females scatter thousands of sticky eggs that adhere to surfaces.
• Post-Spawning: Remove adults immediately to prevent egg consumption.
• Hatching:
  • Eggs hatch in 2–3 days.
  • Fry absorb the yolk sac for a few days before becoming free-swimming.
• Feeding Fry: Start with powdered fry food or infusoria, transitioning to baby brine shrimp.

Health Concerns

Due to selective breeding, Ranchus can be prone to health issues:

1. Ich: White spots from protozoan parasites caused by stress or poor water quality. Treat with medications and stabilize parameters.
2. Velvet Disease: Rust-like patches caused by parasites; treat with anti-parasitic medications.
3. Fin Rot: Bacterial infection causing tissue decay; improve water quality and use antibiotics.

Tips for Success

• Maintain pristine water conditions to reduce stress and disease risks.
• Use a large tank or pond to allow full growth potential.
• Provide a balanced diet to support health and vibrant coloration.
• Observe for early signs of illness and treat promptly.

With proper care and attention, the Ranchu Goldfish can thrive and bring its unique charm to any aquarium or pond setting.