Ranchu are often called the "king of goldfish." They have a rounded body, no dorsal fin, and a wen (the fleshy head growth) that gets bigger with age. They are slow, gentle swimmers, so they need a calmer setup than other goldfish. Here is how to keep a Ranchu healthy.
Ranchu Tank Size
- First Ranchu: at least 20 gallons
- Each extra Ranchu: add 10 to 15 gallons
Adults reach about 6 to 8 inches. They make a lot of waste, so bigger tanks keep water cleaner.
Water Conditions
- Temperature: 68 to 75°F for long-term care
- pH: 7.0 to 7.8
- Ammonia and nitrite: 0 ppm
- Nitrate: under 20 ppm
Note for new arrivals: Ranchu raised in Thailand are used to warm water. When your fish arrive, keep the tank around 76 to 78°F and follow a slow acclimation. You can lower the temperature gradually after they settle in.
Filtration and Water Flow
Ranchu are poor swimmers. A strong current tires them out. Use a gentle filter such as a sponge filter, or a larger filter with the flow turned down or spread out. Strong biological filtration is still a must. Do a 25 to 50 percent water change each week.
Substrate and Decor
- Bare bottom or smooth sand is best. Sharp gravel can hurt their bellies.
- Smooth decor only. The wen is delicate and can scrape or tear.
- Hardy plants like anubias work. Goldfish eat most others.
What to Feed Ranchu
Ranchu have short bodies and are prone to swim bladder problems. Feeding well helps prevent this.
- Sinking pellets so they do not gulp air at the surface
- Soak dry food for a minute before feeding
- Blanched peas now and then to help digestion
- Frozen bloodworms or brine shrimp as a treat
Feed small amounts two times a day. Ranchu are slow eaters, so make sure faster fish are not taking all the food.
Our own premium fish food line includes a sinking pellet made for fancy goldfish.
Tank Mates
Keep Ranchu with other slow fancy goldfish such as Lionchu and Oranda. Avoid fast single-tail goldfish like commons and comets. They out-compete Ranchu for food and can nip their fins.
Common Ranchu Problems
- Swim bladder issues: Floating sideways or upside down. Fast and feed peas.
- Wen infections: Redness or white fuzz on the head. Improve water quality right away.
- Fin rot: Ragged or red-edged fins. Check water and do water changes.
Quarantine every new fish for at least 2 weeks before adding it to your main tank.
Ranchu vs. Lionchu vs. Oranda
These three fancy goldfish are often confused. Ranchu and Lionchu have no dorsal fin. Orandas do. Lionchu usually have the bigger, heavier wen. Browse each group here:
Frequently Asked Questions
How long do Ranchu live?
With good care, 10 to 15 years.
Do Ranchu need a heater?
Not always, but a heater keeps temperature steady, which matters more than the exact number.
Why does my Ranchu swim upside down?
This is usually a swim bladder problem. Fast the fish for a day or two, then feed soaked food and peas.
Can Ranchu live outside?
Ponds can work in mild weather but sudden temperature swings and predators are risks.
Buy Ranchu Online From San Diego
Garage Aquatics imports and ships fancy goldfish from San Diego, CA.
Read our live fish shipping guide before you order.
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