Breeding goldfish in fish ponds and fish tanks

Breeding goldfish can be as simple as leaving them in an outdoor pond to do what hsh do naturally or as complicated as you make it. Specialist breeders have single matings in separate tanks, remove the eggs and cull the fry like any other livestock. You may not wish to breed at all, rather just buy a new one or two when you need them. This section will try to cover the basics but if you become a hobbyist and show you will need more specialist advice, you can achieve this by joining a fish keeping club where you will meet expert fish breeders. 

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Sexing Goldfish – finding their gender

Sexing fish can be hard, their features aren’t as pronounced as humans or many other animals –  but it can be done right in the breeding season. If in doubt, buy a few fish and wait until the breeding season. If you are not in the breeding season there are some indicators but the fish must be sexually mature. These are for more experienced keepers only. They are vent shape, fin shape, abdomen and some breeders claim the midline ridge is an indicator. The best method is to go to known breeders or shops with sexed fish and study the characteristics. I prefer to wait until the fish are sexually active.

Again, with small, relatively cheap fish such as goldfish, if you put 5 in the same space there’s a very good chance you will have a compatible pair of breeding fish. 

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Sexing Sailfin fish

During this period males can be reliably identified once they are in breeding condition. The males keep their streamlined shape while the females begin to get round in the abdomen. This is the area where the eggs are formed. The males also develop small white tubercles (growths) on their gill covers and also on the front edge of the pectoral fin. These growths are used by the male to stimulate the female to make her release the eggs during spawning. These are small and only in these areas. Females can be readily identified when the males start chasing and nudging them on the sides and vent.

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Male with white tubercles on body

If you become a specialist breeder you will want to match specific pairs of fish so it becomes necessary to sex fish. If you are only after some young fish as an activity during the start of your hobby buy four or five fish so you can be sure you have a mix of sexes.

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Gold fish eggs at the bottom of a glass fish tank. Notice the tiny black eyes in the fish eggs


ln ponds, goldfish can be left to their own devices and don’t really require much care or effort if you aren’t serious. You may get a few young from season to season but you need to know that the parents will eat their own eggs, and lots of them, so don’t expect too much. Breeding happens in the warm months and if you want to help this along feed them extra protein such as the live foods. You will need to have some weed in the pond so the eggs have something to stick to after spawning. The fish prefer floating plants but submerged plants will do. You can also just stick some soft branches in the water.

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Some sort of grass is required for fish in outdoor ponds to breed adequately

Remove female fish after breeding.  

Your female goldfish may spawn two thousand to five thousand eggs and will be totally exhausted both by spawning and the male(s). You may need to separate her to stop her from further harassment as females can get badly knocked around. If you do this you can remove the eggs as well to a separate tank or pool. Be careful as the eggs are delicate and need to go straight into water of the same type. Keep this as if there are fish in the tank.

Taking care of eggs

Your young fish (fry) will hatch into this tank so have the filtration and aeration correct at the beginning. You can also set up this kind of tank and move the pair into it, then remove them. This leaves the eggs behind. It is really a matter of choice. The eggs will hatch in about three to four days under ideal conditions which are between nineteen and twenty one degrees. It may take longer if the water is colder. The fry are about one day away from hatching when you can see the eye in the egg.

Other methods of spawning fish ( I prefer the natural method)

Experienced breeders use artificial spawning material such as nylon netting to catch the eggs but this is not necessary at beginner level. You can also hand spawn the fish to get more eggs but I have never done this or felt it necessary to breed my fish. The natural methods have never been a problem and I prefer the ease of this method, both for myself and the fish.

Feeding your fry

When the fry hatch leave the nesting material in as they need something to hang on to and hang out in. they will digest the rest of the egg during this time. After this they become free swimmers and will need to be fed. In a pond they will eat the very minute organisms that live in the pond. In a tank you will need to feed them. You can feed powdered egg yolk, dry sifted fish food or brine shrimp. You can produce your own shrimp or purchase it. Brine shrimp hatcheries can be quite fun to have and produce lots of feed. Some commercial feed products are also available.

Dried egg yolk and brine fish are great sources of food for your newly hatched fry, you can also use bottled food too

Culling to preserve life

One of the hard parts about breeding fish is that you Will have to cull or remove unwanted fish. If only ten percent of your eggs hatch that will still give you over two hundred young. You must be prepared to remove fish that are unwanted. You will need to start when they are about one centimetre long. This will give the good ones more space to grow. First look for damaged or misshapen fins then go to the total shape of the body. Remove any fish with obvious deformities.

You can give them away but you soon run out of friends. Some shops take them but you will get no money. It is easier to humanely cull them. Try not to touch the good ones as they are still very delicate at that age. Just remove the culls. This should continue for all the growth of the fry. Keep removing unwanted fly to give the others a better chance at maximum growth. This is especially important if you are breeding for show or a Specific color or type.

Goldfish fry – try to keep them similar in size to prevent fighting

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