How to Breed Goldfish

Scientific Name: Carassius auratus

Breeding Method: Egg scatterer

Ease of Breeding: Easy

Introduction: Goldfish have been kept in captivity for thousands of years, and are eas­ily bred both indoors and out. They come in many colors and varieties, from egg-shaped orandas to long, lean comets and bubble-eyed celestials. Goldfish prefer cool water and should not be kept in the same tank as tropical species.

Sex Differences: Males typically have pin-sized bumps called tubercles on their gill plates, which turn white when the fish is in breeding mode. Females are usually plumper than males.

Water Conditions: Not critical as long as neither pH nor hardness is extreme and temperature falls somewhere between 60° and 75°F.

Equipment: A spawning tank of at least 30 gallons, preferably long and low to maximize surface area, filled with 6 to 9 inches of water. Temperature should be between 66° and 74°F. Add a half dozen spawning mops and some plants. As fry grow, you'll need one or more 20-gallon long grow-out tanks equipped with sponge filters and heaters.

Conditioning and Triggers: Start with a single pair or a trio consisting of two males and a female who are at least 18 months old. Condition with plenty of frozen or live foods, such as blood worms, brine shrimp, and earthworms. Change about 20 percent of the water a day. Some pairs spawn almost immediately; others take weeks or months. Dropping the water temperature a few degrees overnight, then raising it first thing in the morning, sometimes prompts spawning. Thunderstorms also sometimes trigger spawning.

Spawning: Usually takes place first thing in the morning. The male chases the female, bumping her abdomen and driving her into the spawning mops; a process that may go on for several hours before she releases her eggs. He follows, fertilizing them. Remove the parents when spawning is complete so they don't eat the eggs.

Brood Size: Up to 2,000.

Fry Care: Fertilized eggs turn yellow or amber within a day. Remove any that remain white or grow fungus. (Some breeders add a few drops of methylene blue to prevent fungus.) Fry hatch within a week, depending on water temperature, and become free swimming two or three days after that. Feed three or four times a day with green water or hard-boiled egg yolk and brine shrimp. Do daily water changes, preferably after feed­ing, to maintain water quality. Fry need plenty of room to grow properly; at ten days of age, 100 fry can be kept in a tank with a surface area of 144 square inches, but at a month, the same tank should contain no more than 30 fry. Some breeders say fry devel­op best when temperature is a constant 68°F.

Special Notes: Getting fish in condition to spawn is the hardest part of breeding gold­fish, since in nature they go through a winter dormancy period, then spawn as the water warms up. While this isn't exactly recommended, some breeders have mimicked this by cooling their fish down gradually in the refrigerator, then allowing them to warm back up!