How to Tell if a Goldfish Is Pregnant

Co-authored by Craig Morton

Last Updated: September 14, 2024 Approved

When goldfish are preparing to lay eggs (otherwise known as “spawning”) the goldfish is said to be pregnant. If you believe your goldfish may be preparing to spawn, there are several ways to find out. First, try to figure out whether or not the conditions are right for your fish to spawn. Then, try to observe "pre-spawning" behaviors in both your male and female fish. Although it is rare, it is possible to purchase a pregnant goldfish. Otherwise, your fish will only become pregnant if there are both male and female fish present.

Part 1

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Checking the Conditions

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Find out if your fish is female. The best way to find out the sex of your goldfish is to ask when you buy the fish or to consult a vet. That said, females goldfish typically have plump bodies. When viewed from above, you can usually notice fuller bellies on the females, and slender midsections of the males. Also, the female pectoral fins (located just behind the gills) are shorter and rounder than those on males.^{[1]
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- Additionally, goldfish will generally not lay eggs until they are at least one year old.
If your goldfish is kept outside, it will only spawn during the spring. If your goldfish has always been kept inside, it could spawn at any time of year. Think about what season it is when determining if your outdoor goldfish is pregnant.^{[2]
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Goldfish are most likely to breed in water that is around 72 °F (22 °C). If you believe your goldfish may be preparing to spawn, check the temperature of your water to see if the temperature right.

Part 2

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Looking for Pre-spawning Behaviors

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Look for spawning tubercles on your male goldfish. When your male goldfish are ready to spawn, they will develop tiny white bumps known as “spawning tubercles” around their heads, gill covers, and pectoral fins. If you notice these white spots on your male fish, there is a greater chance that your female fish may be pregnant.^{[3]
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- Spawning tubercles may be hard to see. If you do not see these, it doesn’t mean that your fish isn't pregnant.
When they are preparing to spawn, the male fish may chase the female ones, in a dance sometimes called the “spawning chase.” In many cases, this behavior is more obvious than spawning tubercles (which can be hard to see).^{[4]
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Pay attention to your goldfish’s activity level. When goldfish are about to lay eggs, they usually start to move more sluggishly. Take note if your goldfish is moving slowly or seems to have trouble getting around.^{[5]
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- You may also notice your goldfish “nesting,” or spending most of the time hiding near shelters or plants.
When are fish are preparing to spawn, they will sometimes refuse food. If your goldfish isn't eating as much, it is possible that they may lay eggs soon.^{[6]
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Note the size of your goldfish’s body. Female goldfish are generally a bit rounder than male goldfish. When your female goldfish is about to lay eggs, the size of their belly may grow even larger, and stick out a bit.^{[7]
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- Just like the spawning tubercles, in some fish this can be quite noticeable, yet in others, you may not see it at all.

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Do goldfish need cold or hot water?

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Goldfish should be placed in cool or cold water, but never in hot water.

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What do the eggs look like?

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The eggs are small in size at about 1 mm. They are also clear.

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What if my goldfish is urgently looking for a place to lay, but there are no plants or sponges? I put in a large seashell, which she ignored. What else can I do?

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Try putting in plants if she won't accept a seashell. Also, remove the seashell, because seashells dramatically change the water chemistry, and can easily kill your fish.

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