Celestial Goldfish Breeding Guide

How to breed the Celestial goldfish (Carassius auratus), an egg-scattering fancy variety triggered by spring temperature change, with upturned eyes.

Overview

The Celestial is a domesticated variety of Carassius auratus, distinguished by a double tail and a breed-defining pair of upturned, telescope eyes with pupils gazing skyward. Like all goldfish it is an egg-scatterer. The variety is produced by selective breeding, and some extreme fancy goldfish are much less hardy than forms closer to the wild original; the permanently skyward eyes leave the fish with very poor sight, so breeding requires close attention to feeding and tank-mate selection.

Conditioning

Goldfish reach sexual maturity only with sufficient water volume and the right nutrition. Mature, healthy adults are conditioned before the breeding season. The optimum temperature for goldfish is between 20 and 22 °C (68 and 72 °F); temperatures under about 10 °C (50 °F) are dangerous to fancy varieties and temperatures over 30 °C (86 °F) can also cause harm.

Breeding Setup

Provide dense aquatic vegetation such as Cabomba or Elodea, or a spawning mop, because the eggs are adhesive and attach to this material. A separate spawning tank lets the adhesive eggs be protected, as adults may eat young they encounter.

Spawning Behavior & Trigger

Breeding usually happens after a significant temperature change, often in spring. Males chase gravid females and prompt them to release their eggs by bumping and nudging them. The female then scatters adhesive eggs across the plants or spawning mop.

Egg & Fry Care

The eggs hatch within 48 to 72 hours. In their first weeks of life the fry grow quickly, an adaptation born of the high risk of being eaten by adult goldfish, other fish and insects. Within a week or so the fry begin to assume their final shape, although a year may pass before they develop mature goldfish color; until then they are a metallic brown like their wild ancestors.

Common Challenges

Selective breeding for the upturned celestial eyes leaves the fish with very impaired sight, which complicates feeding and competition at spawning. Some highly selectively bred goldfish can no longer breed naturally due to their altered shape, and heavy culling of fry is needed to keep only those that express the breed-defining double tail and skyward eyes.