Ranchu Goldfish - our pick

A dorsal-less goldfish that waddles through water on a rounded belly.

Hand-picked Ranchu goldfish for sale—our pick for healthy, characterful fancy goldfish with a rounded body, wen growth and peaceful coldwater charm.

• Water conditions: Ranchu goldfish are coldwater fancy goldfish and do best in a stable, well-oxygenated aquarium with plenty of biological filtration. Aim for a temperature of around 16–24°C, with 18–22°C being a comfortable long-term range for most indoor setups. Avoid sudden temperature swings, overheating and cold draughts. pH should be around 6.5–8.0, and general hardness can range from soft to moderately hard, roughly 5–15 dGH, provided conditions are stable. Ammonia and nitrite must always read zero, and nitrate should be kept low through regular water changes—ideally below 20–40 ppm. Ranchu appreciate high dissolved oxygen but dislike strong currents, so use a filter with a gentle outflow, an air stone on low power, and a spray bar or diffuser where possible. A mature, fully cycled tank is essential; never add a Ranchu to a new or uncycled aquarium.
• Tank size and setup: Although Ranchu are compact and rounded, they are messy fish with a heavy bioload. A single adult Ranchu needs a tank of at least 120–150 litres, with 45–60 litres added for each additional fancy goldfish. A long, wide footprint is far more valuable than height because Ranchu are poor swimmers and need horizontal space to browse and turn comfortably. Use a smooth sand substrate or a bare-bottom setup for easier cleaning; avoid sharp gravel, rough rocks and tight caves that can damage the wen or fins. Provide gentle filtration, good surface movement, a secure lid and simple, smooth decorations. Ranchu are curious and will sift through sand, so avoid small gravel that can be accidentally swallowed. Keep the tank away from direct sunlight and heat sources to maintain a stable temperature.
• Suitable tank mates: The safest and most successful approach is a species-only fancy goldfish aquarium. Other slow-swimming fancy goldfish of similar size, such as Orandas, Pearlscales and other Ranchu, can work well in a sufficiently large tank with matching water conditions. Avoid common goldfish, comets and shubunkins—they are faster, more competitive feeders and need far more swimming space. Do not house Ranchu with tropical fish that require warm water, fin-nipping species, aggressive cichlids, crayfish, crabs or small fish that could be eaten. Bottom-dwelling fish such as common plecos are not ideal because of waste output and attachment risks. If you choose tank mates, quarantine them first, research their temperature and diet needs, and always provide extra filtration and space.
• Feeding habits: Ranchu are enthusiastic but clumsy feeders and benefit from sinking foods rather than floating pellets, which can encourage gulping and swim bladder problems. Feed a varied diet of high-quality sinking fancy goldfish pellets, gel foods, daphnia, brine shrimp, bloodworm as an occasional treat, and blanched vegetables such as shelled peas, spinach and courgette. Offer two to three small meals daily, giving only what the fish can clear in a few minutes. Pre-soak dry pellets to soften them and reduce the risk of constipation. Ranchu have rounded bodies and can become overweight, so avoid overfeeding and monitor body shape. A weekly fasting day can help digestion, but adjust according to condition and age. Remove uneaten food promptly to protect water quality.
• Care and maintenance: Carry out weekly water changes of around 25–50%, depending on stocking and nitrate levels, using a gravel vacuum or siphon to remove waste from the substrate. Test ammonia, nitrite, nitrate and pH regularly, and rinse filter media only in tank water to preserve beneficial bacteria. Ranchu are delicate fancy goldfish and are prone to swim bladder issues, constipation, fin rot and bacterial infections when water quality slips. Observe them daily for changes in buoyancy, appetite, fin posture and wen condition. Handle them as little as possible, and always acclimatise new arrivals carefully—preferably by drip acclimation—before releasing them. Quarantine new fish and plants to reduce disease risk. Because Ranchu lack a dorsal fin and have a curved back, they are slower and less able to compete; choose a calm setup and avoid strong flow. With stable water, gentle filtration, a balanced diet and regular maintenance, a healthy Ranchu can be a rewarding centrepiece for a coldwater fancy goldfish aquarium.