Ryukin Goldfish

Ryukins are a Japanese-bred variety of fancy goldfish with a distinctively tall, arched back and a deep, rounded body that gives them an almost egg-like silhouette when viewed from the side. Those flowing double tails and paired anal fins are what draw most people in, and they're available in a wide range of colors including solid red, red and white bicolor, calico, and a rich chocolate brown. They're generally considered one of the sturdier fancy goldfish options compared to, say, orandas or ranchus, though that doesn't mean they're maintenance-free.

They do best in cooler water between 15 and 24 degrees Celsius, which rules out the typical tropical community tank setup. Filtration is where most beginners underestimate them. Goldfish in general are messy, and ryukins are no exception. You want turnover running at least 8 to 10 times the tank volume per hour, and even then you'll be doing weekly water changes of 25 to 30 percent. A 114-liter tank is the minimum for one fish, but two ryukins really need closer to 190 liters.

Diet should be varied. Quality sinking pellets or gel food work well day to day, supplemented with blanched vegetables and occasional protein treats like daphnia or brine shrimp. Their compressed body shape puts them at risk for swim bladder problems, so pre-soaking any floating foods before feeding helps reduce that risk considerably.

They're peaceful fish with no real aggression to speak of, making their tankmate requirements more about what won't bother them than what they'll bother. Their long fins are an easy target, and their slow swimming style means faster fish will eat all the food before they even get close. Browse actual ryukin tank builds to get a feel for how to set up filtration and decoration for these fish.