Ryukin Goldfish Breeding Guide

How to breed the Ryukin goldfish (Carassius auratus var. Ryukin): spring spawning trigger, egg scattering on plants, ~4-day hatch and selecting the dorsal hump.

Overview

The Ryukin is a selectively bred variety of the goldfish, Carassius auratus, recognized by its short deep body, high dorsal hump behind the head and double tail. It spawns with the same egg-scattering biology as other goldfish; the breeding challenge is producing offspring with the characteristic body depth and dorsal profile.

Sexing

Mature goldfish are sexed most reliably in the breeding season, when males develop small white breeding tubercles (stars) on the gill covers and leading pectoral-fin rays. Gravid females become noticeably rounder and deeper-bodied. Tubercles are typically present from spring through autumn.

Conditioning

A breeding programme normally starts in early spring with the water warmed to about 17 degrees C (63 degrees F), with fish well reconditioned after the cooler winter. Breeders commonly spawn one female with two or three males to spread the chances of fertilization, and add plenty of fine-leaved spawning medium such as hornwort or a spawning mop.

Spawning Behavior & Trigger

Spawning is triggered by a significant temperature rise in spring as the water approaches about 20 degrees C (68 degrees F). Males chase the gravid female and prompt her to release eggs by bumping and nudging. The adhesive eggs scatter and stick to plants such as Cabomba, Elodea or a spawning mop.

Egg & Fry Care

Because goldfish eat their own eggs, parents must be removed as soon as spawning is over (the eggs are adhesive and cannot easily be moved). The eggs hatch in about four days and the fry become free-swimming roughly 24 hours later, which is when feeding begins. Fry are an undistinguished metallic brown and may take a year before developing mature goldfish coloration.

Common Challenges

Few fry will show an ideal Ryukin shape, so breeders cull heavily and keep only those developing the desired body depth, dorsal hump, tall dorsal fin and double tail. While some extreme goldfish varieties can no longer breed naturally due to their altered shape, the Ryukin generally remains capable of natural spawning.