Ranchu Goldfish

Called the 'king of goldfish' in Japan, the Ranchu is a heavily bred fancy goldfish variety developed over centuries of selective breeding in East Asia. Unlike most goldfish, it carries no dorsal fin at all, giving it a smooth, arched back that curves dramatically from head to tail. The wen, a fleshy growth covering the head and cheeks, is one of the most defining traits breeders evaluate, and in show-quality fish it can be quite dramatic. They come in red, white, orange, calico, and bi-color forms, and a subtype called Top View Ranchu is specifically bred to look stunning when viewed from above rather than the side.

Keeping these fish well is genuinely challenging. Their egg-shaped body and absent dorsal fin leave them wobbling through the water in that characteristic waddle, which is endearing but means they struggle with any meaningful current. Filtration needs to be powerful enough to handle their enormous waste output while keeping flow gentle enough not to stress them.

Water quality is non-negotiable. Ammonia spikes hit them hard, and without consistent maintenance they're prone to bacterial infections, fin rot, and swim bladder problems. Temperature-wise they do best in cooler water, typically between 10 and 23 degrees Celsius, and actually benefit from seasonal temperature drops if kept indoors year-round.

They're omnivores but should get a high-quality sinking pellet as the base of their diet since surface feeding causes them to gulp air, which contributes to buoyancy issues. Blanched vegetables and live foods make good supplements.

For all their quirks and demands, Ranchu are deeply personable fish with individual characters you'll notice quickly. Browse real tank builds featuring these fish to see how experienced keepers balance filtration, flow, and decor to make them thrive.