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Breed those goldfish. Guide to Comet Goldfish Breeding.

Comet Goldfish Breeding

The comet goldfish was originally developed by Hugo Mulertt, an employee of the United States government back in the 1880’s. The first ever comet goldfish were actually in ponds at the United States Govt. Fish Commission, located in Washington D.C. There are two different types/variants of comet goldfish. The comet goldfish can grow up to 13 inches, and live up to 15 years given the proper care and tank. If you keep your fish in a fishbowl, this type of goldfish may only live a couple of months, so try to get something bigger as soon as you can.


Types of Comet Goldfish

  1. Sarasa Comet – These are the red and white ones that resemble koi, they have fins that are long and flowing, and they are described as being hardy. The sarasa is originally from China, but it’s name sarasa is of Japanese origin.
  2. The Tancho Single-Tail – These are the silver ones with red on their head.


The goldfish in general belong to the summer spawning variety, meaning that if your fish are outdoors, they will not start the process until the water is warmed up by the sun nice and warm, but breeder begin preparing the tank for the propagation in the late winter, when the fish come up to the top and start being more active. The optimum temperature for the water in a comet tank is 50-75 degrees Farenheit, but it’s usually a good idea to let the water go naturally, unless you’re having problems with heating or air conditioning, and you have to regulate the temperature due to extreme circumstances. The fish are cool water fish, and can suffer permanent nerve damage if the water heats up too much. The good thing about comet goldfish, is that you can breed them inside, or just leave them in the pond, and let them do their thing naturally. They can be a little bit more difficult to breed, unless you’re hand stripping them. It is recommended that you wait until your comet friends are a coupe of years old, and if you get them from someone else after they look more mature, just wait a year to be on the safe side. Generally, you want to wait until they are 3-5 inches long, or 3-4 years old for best results. Breeding is commonly and professionally done in trio aquariums, (three section tanks) but you can breed them in a regular one, just remember to remove the adults after eggs are laid. Always prepare a separate tank ahead of time, so that the parents will not go into shock when you move them after the eggs are done. You also want to pick the healthiest looking specimen, so you can have the best chances at viable, pure breed babies. All of a fishes qualities are inherited by the young, and this is why you need to be selective. If it looks like a fin has taken an injury, and grew back funny, you can still use these if they look perfect otherwise.


comet goldfish breeding


How to Tell Male Comets From Female Comets

There are slight visible characteristics that you can look for when sexing your comet fish. This is what to look for in males.

  1. Males have white “pimples”, or bumps, better known as “denominated tubercles” in the tissue on their gill plate, and this trait is an indication that they are ready to breed. When the tubercles secede, they are no longer viable as a mate.

This is what to look for if they are female.

  1. Females are normally a little fatter than males. (This makes identification of females a little tough, until you get used to it, I would look for the males and separate them, as they are much easier to tell apart.



  1. The rumor that you can tell the sex of a goldfish by a small, dorsal fin is false. These grow sporadically on males and females.
  2. The females must be picked when their stomach starts to fatten. This indicates the ripening of the eggs.
  3. Some goldfish are sterile, either for a season, or for their whole life, so don’t get frustrated if this messed up your plans, just try again next season.
  4. It is important to keep the water clean, and the best filter for comets is a canister filter, but if you have one that clips on the back, just clean the media and/or sponge frequently.


You are going to want at least a 10-15 gallon tank. Try to find something short and long. It is good practice to place a couple of live plants I the tank, like java moss, or duckweed. This provides a place for the female to drop eggs, and prevents the parents from eating them all. In the wild, the parent fish of the comet species are prone to eat their fry, (eggs) limiting the number in future generations. When sexing the fish to tell if they are male or female, you want to place about 3 females to 4 males, because if you outnumber the female comet fish more then that, there will be too many eggs for the males to cover, and this will cause infertility problems. It is only recommended to put 4-6 fish in a tank at a time for spawning. If you want to induce spawning, this can be done by lowering the temperature for about a month, and limiting light to the tank to eight hours a day. This will trigger spawning After spawning, gradually raise the temps over a couple of days, to about 70-75 degrees, and increase the exposure to light to 12 hours a day. High quality food, like brine shrimp, or frozen bloodworms, and dropping the temps slightly in the tank have also been proven to prompt the fish to mate. The adults should be removed from the tank as soon as the eggs are laid, and it takes about 2 days for the babies to hatch, and about to more before they are fully free swimming.


After Eggs Are Done

After your baby comets come out, you can feed them infusoria, baby brine shrimp, or commercially available fry food for best results and growth. After you are done and your fish are getting bigger, if you plan on keeping some, it is recommended to upsize your tank to accommodate the extra fish.


I hope you find this article useful!!! Happy comet goldfish breeding!!!

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