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Breeding Goldfish, Hand Spawning

Hand Spawning Goldfish – The Mechanics And The Reasons

by Dr. Streamson Chua


Early one morning, you take a look at the commotion in your display tank of show quality goldfish. The fish are swimming faster than you’ve ever seen before and there are thousands of eggs over everything. You think: If I could raise a few of those eggs, I could make a tidy bundle by selling them. So, you move the fish or you move the eggs. Unfortunately, your tank has power filters that turn over the water at 10 times per hour and the water is cleaned with ultraviolet lamps. If you’re lucky, one egg out of a hundred is fertilized and hatches. So, one solution to this problem is to hand spawn the fish and raise the eggs in a separate tank. There are actually several reasons for hand spawning goldfish. Here is a partial list:

  • The fish are spawning in a show tank or any other tank that is not set up for raising fry.
  • There is a need to know the parents of the fry.
  • The male(s) do not chase well and have demonstrated low fertility in previous spawns.


The male and female fish should be housed in the same tank since the males’ sexual development is influenced by the females. The fish need to be prepared for spawning by feeding them heavily over several weeks. Feeding heavily mean three to four meals every day, providing them with as much as they will eat over 15 to 30 minutes. Females will develop a gravid look, as if they are becoming pregnant. This is due to enlargement of the developing eggs. Males will develop white tubercles on the gill covers and the leading edges of the pectoral fins. The tubercles can also be felt as a sand paper feel.

Goldfish will spawn according to their own schedule although you can help them along. Keep the water around 70°F with frequent small water changes (about 15% two to three times a week). This is actually necessary for the health of the fish due to the extra feeding. When the females look really full, you can try to induce them to lay eggs. I have found that egg laying occurs about two to three days after a low pressure system brings a thunderstorm and heavy rainfall. I take advantage of the change in barometric pressure by performing large water changes (50%) every day for three days. Since I work during the week, I look up the weather forecast for the week and start water changes on Wednesday night or Thursday morning so that the fish will spawn around Saturday or Sunday. If this doesn’t work, wait a week until the weather forecast looks good. Keep trying until they spawn. Since well-fed females will spawn every 7-14 days, it isn’t a disaster if you miss the first spawn. The second spawn can be timed so that you will have a chance to catch the fish in the act, so to speak.

The Mechanics

The Container

On the second day after starting the water changes, make sure to wake up a little before or just at sunrise. This is because goldfish spawn early in the morning, just around sunrise. You might see just a few eggs (if the female just started) or thousands of eggs (if the spawning is nearly over). I use a plastic shoebox made of polycarbonate for the hand spawning since polycarbonate sinks in water due to its buoyant density. A shoebox of polypropylene (the box will have a PP symbol inside the recycling symbol) is acceptable but the box will need to be weighed down since polypropylene has a tendency to float.

The Male

Get the male into the box along with enough tank water to fill the box with about three inches of water. Hold the male with both hands, left hand over the head and right hand near the ventral fins, making sure that you can see the vent clearly. If you’re left-handed like me, reverse the position of the hands. Using your right hand, gently squeeze the male about two-thirds down the length of the body so that you see the milt coming out. The milt is a white fluid that looks like milk. Swirl the milt with your hand or the fish’s tail. A very fertile male will provide so much milt that the water will become cloudy. (A male that is not kept with females does not produce any milt, in my experience.)

The Female

At this point, bring the female into the box by transferring her in your hands or inside a small quart container. I would recommend that you wait until the female has released most of her eggs. The reason for this being the extreme fragility of a gravid female. I have lost several females by hand spawning them too early in the spawning process. The fish died several weeks after spawning from peritonitis, probably as a result of ruptured ovaries. Hold the female in the same position as you did with the male. Even more gently than you did with the male, squeeze the female’s abdomen very gently until you see a small stream of eggs coming out. Most of the time, the female will squirm in your hand and the eggs will come streaming out without any effort on your part. Immediately swirl the eggs around with the female’s tail. The reason is that the eggs swell and become sticky upon exposure to water. If the eggs are not separated, they stick to each other and do not develop properly. Collect about 300-500 eggs per shoebox. Another male can be used to fertilize the eggs of the same spawning female if you wish to test the qualities of two males. Leave the parents alone for about 5-10 minutes to recover. Gently transfer the parents back to their home tank. The eggs should be rinsed with fresh tank water three to four times to remove the excess milt and residue from the parents.


Place the shoebox with the eggs in a 30 gallon tank (or larger) that contains established sponge filters along with an air stone to provide circulation inside the shoebox. Under no circumstances should the eggs be incubated in the small quantity of water that the shoebox will hold – the fry will develop into bottom swimmers or worse. The water should be kept at a constant 70°F for optimal development. Development of the fertilized eggs can be followed under a low power microscope – the first cell division occurs within 30 minutes of fertilization. Bad eggs or unfertilized eggs will become opaque in about 8 hours and develop fungus. The fungus development can be a problem if the fertilization rate is low but the fungus problem can be minimized by running the water through an ultraviolet lamp for the first 48 hours of incubation. My system is to pump the water through a UV lamp at about 200 gallons per hour for a 30 gallon tank with an 8 watt lamp. The ideal system would be to run the water with an airline at low flow rates such that the fry are not subjected to high flow rates. If a lot of eggs hatch (>300 eggs), there will be a release of egg contents that will make the water cloudy and smelly. The water needs to be changed and I perform two 50% water changes on the same day with a siphon that has a sponge over the intake end to prevent losing any fry. At this point, leave the fry alone for about two days until they are free swimming and ready for their first meal.

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Dr. Streamson Chua - 10/24/05 - Viewed 88689 times.

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