1. Plan A Year Ahead
Goldfish can breed at the age of one to two years old. If you are planning to breed goldfish, it’s important to raise them for at least a year before deciding to do so. If you have a young goldfish, you can also watch for illnesses and genetic failures that will occur in the goldfish as it matures. This will help you to see the genetic potential of the goldfish by their health, size, coloration, and body shape.
Keep an eye on potential fish you wish to breed, and try to identify them by July or August (goldfish are spring spawners, and prospective parents should be identified by autumn of the previous year). It is a good idea to keep records on any health issues and problems that may occur in your goldfish so you have a good idea of which specimens will make great breeding stock.
2. Seek Professional Input
Once you have identified the fish you wish to breed, have an aquatic veterinarian come and inspect your fish. Alternatively, if you’re not sure which fish should be bred, it’s best to let your veterinarian decide for you. Remember that a fish that looks appealing might not have the best traits of a robust breeder.
The ideal ratio for spawning goldfish is 3 males to every female. If you haven’t sexed your goldfish, you should ask your veterinarian to do so. Your veterinarian may also run blood tests on your fish and advise you on breeding compatibility.
Please note that the health of your female goldfish is very important, as they can easily get injured during the spawning season. If you have a beloved female goldfish, it is best to not breed her.
It is also best to discuss the option of artificial insemination or hand spawning with your veterinarian at this point; many aquatic vets are able to provide this service for a fee. Though it requires additional monetary investment, it minimizes the risk of injury for female fish and increases the number of eggs that are fertilized.
3. “Clean” Breeders
You would want to place the breeding stock in their own large, cycled aquarium. Before doing so, provide each fish with a “cleaning” cycle by placing them one by one in a 5-gallon aquarium and adding in a combination of Formaldehyde, Copper Sulfate, and a broad-spectrum antibiotic (prescribed by your veterinarian).
The dose of Formaldehyde and Copper Sulfate should be discussed with your veterinarian, as the amount you need will vary depending on the concentration of the product you have. The duration of their exposure to the cleaning process should also be discussed with your veterinarian. It is recommended to have your veterinarian perform this procedure for you.
4. Condition In Aquarium
Once your breeders are in their aquarium, it is important to begin conditioning them with foods such as brine shrimp, worms, and a high-quality pellet.
Important: Do not change their diet abruptly, but rather add these food items into their diet gradually.
It is best to feed your goldfish small amounts of food several times a day (three to four times) when conditioning them this way. When feeding your goldfish for the purposes of breeding them, you should feed them as much as they can eat in a few minutes. It is very important to not let leftover food in their aquarium, as this may spoil and degrade the water quality of your breeders’ housing aquarium.
Live food fed to breeders should be sourced from a reputable breeder, as feeding poor-quality live food offers lower nutritional value and may introduce unwanted pathogens into your aquarium.
Your breeders will need to be constantly conditioned from their selection day up and even after they are done spawning, as the process is quite draining on their bodies.
5. Simulate Winter
As goldfish are coldwater fish, they spawn in the springtime. Waiting for seasonal changes can be cumbersome and when breeding goldfish, it’s best to use a chiller to manipulate the temperature.
Winter can be simulated by gradually dropping the temperature in their aquarium to 10 – 12°C (50 – 54°F). You should only decrease the temperature on your chiller by 1 – 2°C (1.6 – 3°F) per day.
Note: your fish will naturally stop eating as temperatures drop and go into a state of near hibernation, called torpor.
6. Simulate Spring
When you are ready to breed your fish, it’s time to simulate springtime. This time, you’ll need a heater to slowly increase the temperature in their aquarium by 1 – 2°C (1.6 – 3°F) per day until you reach 20 – 23°C (68 – 74°F). This process takes about a week or so.
7. Isolate Best Breeders
Begin to identify prospective breeders in your breeder tank. Males that are ideal for spawning should develop small white dots on their gills and heads (known as tubercules), be strong swimmers, and should show interest by chasing females around. Females that are ideal for breeding should be larger than males, and should slowly turn plump.
Isolate a group of 3 males and 1 – 2 females in a 20-gallon spawning aquarium. Ensure it is cycled and maintained at the “spring” temperature.
Important: A 20-gallon aquarium cannot sustain 4 – 5 spawning goldfish for a long period of time and needs daily partial water changes of 20 – 25% to maintain water quality.
8. Wait For Eggs
Observe your females in the spawning tank, as the stimulation from the males eventually makes them drop their eggs, which stick onto the surfaces of the spawning tank. They usually drop their eggs on the plants in the spawning tank.
Once a female drops her eggs, the males fertilize them by releasing their sperm into the water (fertilization is done externally).
9. Remove Adults or Mop Eggs
Remove the adults from the spawning tank, or move the eggs using a spawning mop. You might be able to identify fertile eggs from infertile ones:
- Infertile: The eggs will go a deep white color and have no black dots signaling the eye development of the goldfish in the egg. They will begin to rot after a few days and produce a fluffy fungal coating. The eggs should be disposed of with warm water and a methylene blue solution in the breeding tank.
- Fertile: The eggs will be a transparent pearl color and have black dots as the goldfish’s eyes develop. The eggs will hatch after a few days and will even show the outline of the fry if a torch is shone on them.
Eggs take 4 – 7 days to hatch; eggs that don’t hatch after 8 days are considered infertile. Infertile eggs should be removed from the aquarium, as they will rot and degrade water quality rapidly.
10. Monitor Fry & Care For Adults
Newborn fry can be fed baby brine shrimp or other foods small enough to fit in their mouths. You can begin the process of raising fry soon after they’ve hatched. Congratulations on your spawn!
Please note that you should also keep an eye on your spawning fish. Females may get injured during the mating process and might require additional care.
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