Goldfish Breeding: What You Need To Know

goldfish breeding and preparation for fry
Preparation for the fry is important for their survival – separate tank, filtration, food

The common goldfish can be credited with giving most people their start in the fascinating hobby of keeping pond or aquarium fish. It is a hardy cold water species that is relatively undemanding in water quality or temperatures.

Goldfish facts

Goldfish are quite placid fish that can be kept either in aquariums or outdoor ponds. They have an average life span of ten to fifteen years.

Goldfish are the product of centuries long selective breeding. The many varieties of colorful ornamental goldfish evolved from humble brown wild carp that were reared for food as early as the Tang Dynasty (618-907).

Selectively breeding goldfish over the centuries has resulted in a wide number of goldfish varieties that have characteristic forms, scale type and colors.

The hardy nature of the common goldfish instills a great deal of confidence in the budding aquarist by its ability to survive and flourish during its owner’s early fish keeping days. Many hobbyists “graduate” to flashier more exotic varieties of goldfish. Plain or fancy, mature fish in their care often spawn with or without their keeper’s attention or aide.

Goldfish breeding facts

Raising the spawn to maturity is often a challenge for fledgling fish keepers. Successfully breeding goldfish and rearing of fish, however is well within the scope of average fish fanciers once the basics of goldfish reproduction water requirements are understood.

  • All goldfish varieties reach sexual maturity at the age of one year if given a proper diet and enough space to thrive. First time breeders should take advantage of reading the descriptions of the ideal specimen of the chosen variety. Each variety has specific physical traits which if present exemplify that variety of fish.
  • Variety faults, such as split tails in fancy tailed varieties should be avoided. A general rule of thumb is buy the best potential breeding stock available.
  • To enhance success rate for breeding goldfish, more males than females should be kept with the usual ratio being two males for every female.
  • Novice breeders are advised to stick to the least extreme forms of fancy goldfish. All too often these exotic types cannot breed on their own and must be bred artificially by ‘hand stripping’ the fish of their eggs and milt. The process of hand stripping, while ensuring a breeding can harm valuable breeding animals if done incorrectly.
  • When mature, goldfish can be sexed fairly easily. Sexually mature males develop breeding tubercles on their gill covers (operculum) and along the first ray of the pectoral fins. Females are distinguished by their more plump generous bodies that were designed to carry their maturing eggs which they will release and scatter during mating.

Water temperature for goldfish breeding

In the wild, sexual reproduction takes place after winter water temperatures rise and daylight lengthen. Goldfish breeding occurs at a temperature of 10 to 26 degrees Celsius. The optimum temperature to ensure breeding success is 20 degrees celsius. In captivity, the hobbyist can artificially replicate the natural seasonal changes by gradually increasing tank temperatures.

Prior to breeding goldfish, the hobbyist should prepare a nursery tank using aged water from the tank in which spawning will take place.

goldfish breeding
Prepare for the needs of the fry for best chance of their survival – feed brine shrimp eggs to the fry

This tank should be filled to a depth of six inches. Water temperatures in the hatchery tank should be regulated to achieve an optimum hatching temperature of 21 degrees Celsius.

Gentle filtration and aeration using a sponge filter and air stone will ensure water quality throughout incubation and hatching.

A string mop should be provided for the fertilized eggs to adhere and develop upon. The use of methylene blue in the nursery tank to retard or discourage fungus growth is highly recommended.

Goldfish Breeding Behavior

Tank temperatures are now conducive for breeding goldfish and mating behavior will soon be observed. Males will begin a “spawning chase” in which females will be pursued and nudged to release their load of goldfish eggs.

Females in top breeding condition can lay between five hundred and a thousand eggs over a period of time. She will produce several smaller batches with the first batches being the most fertile. As the batches are released, the male will immediately fertilize them by spraying them with his sperm or “milt”.

The Nursery

goldfish breeding
fertilized eggs should be transfered to nursery tank

After the breeding activity has ceased, the fertilized eggs should be transferred to the nursery tank. Eggs should be carefully inspected so that infertile eggs can be disposed of promptly. The difference between a fertile and a non-fertile fish egg is readily apparent.

Fertile eggs are clear in appearance,while infertile eggs are generally cloudy. Goldfish fry will hatch between 24 to 48 hours at 21 degrees Celsius.

Once the fry hatch, they will have a fully developed yolk sac from which they will draw nourishment.

They do not need to be fed at this point in their development. The young fish will sink to the bottom of the tank (this is normal) and should not be disturbed. During the next couple of days, they will completely absorb this sac, develop an air bladder and develop the ability to rise to the top of the tank and free swim.

Free swimming usually occurs within 48 hours and the goldfish fry are ready to be fed. Fry can be fed from a commercial product or a homemade ration of a fine paste of oatmeal or hard-boiled eggs.

Click here to buy a nursery tank.