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How to Tell If a Goldfish Is Pregnant: 6 Signs

Sarah Psaradelis

By Sarah Psaradelis

pregnant goldfish together with other goldfish in the water

Whether you are planning to breed your goldfish or simply want to check if your goldfish is pregnant, then this article is for you. Unlike live-bearing fish like mollies or guppies, goldfish develop eggs inside of their body when they are mature. The eggs will then be deposited for a receptive male goldfish to fertilize. While it can be referred to as goldfish pregnancy, the process of developing and producing eggs for external fertilization is called spawning.

This means that goldfish pregnancy can be quite different from mammalian animals and live-bearing fish. However, there are still signs to look out for that can indicate whether your goldfish is carrying eggs or not.

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The 6 Signs the Goldfish is Pregnant

1. Distended Stomach

Although female goldfish typically have a significantly rounder belly than males, a pregnant goldfish will have a noticeably distended stomach than the rest. A few days before a gravid female deposits her eggs, you may notice that her belly starts to balloon out. This is usually a good indication that the female is getting ready to spawn, and you should ensure that the spawning environment is ideal.

Gradually increasing the temperature in the tank by 2–3 degrees may help encourage spawning behaviors in your goldfish. A pregnant goldfish with a very swollen belly will likely deposit her eggs over plants, rocks, and on the substrate. Depending on the variety of goldfish you have, the belly may swell up two to three times more than its original size.

While a distended stomach can be a sign that a female goldfish is about to spawn, it can also indicate certain health problems. Dropsy, tumors, and overeating can also make your goldfish’s stomach look larger than normal. If dropsy is the case, your goldfish will have visible scales that protrude from their bodies. This is known as “pine-coning”, and a goldfish with dropsy is very difficult to treat.

nymph goldfish at the bottom of the tank
Image Credit by: dien, Shutterstock

2. Lopsided Belly

When a female goldfish’s belly swells from a lot of eggs, you may notice that the belly looks lopsided. This can be seen if you view the goldfish from above, but you won’t always be able to spot the lopsided belly. The lopsidedness is likely from the large number of eggs that the goldfish is producing and getting ready to deposit. You may also be able to feel the clusters of eggs through the belly, especially a day or two before she deposits them.


3. Check Males for Spawning Tubercles

Female goldfish generally develop eggs and spawn when they are kept with mature male goldfish. One way of determining if your female goldfish could be pregnant is to determine whether the males in the same aquarium are showing spawning tubercles.

Although both male and female goldfish can get spawning tubercles, it is more noticeable in mature male goldfish. These tubercles will look like small white bumps near the goldfish’s gills and pectoral fins. These spawning tubercles or “breeding stars” may indicate that the male goldfish is ready to spawn with a reciprocating female.

So, if you have begun noticing that your male goldfish has developed spawning tubercles and there is a female goldfish in the tank with an abnormally large belly, she is likely pregnant. However, even if you don’t see it, it doesn’t mean that your female goldfish is not pregnant.

male goldfish black background
Image Credit by: HamsterMan, Shutterstock

4. Restricted Movements

When a pregnant goldfish’s belly starts to balloon out, you might notice that she has difficulty swimming normally. This is because her larger belly weighs her down in the water and she may look quite uncomfortable the next few days before depositing her eggs. If you have a filter that produces a strong current in the water, a heavily pregnant goldfish can get stressed trying to swim. If this is the case, adjusting the flow to a lower setting can make it easier for her.

Alternatively, you can place your female goldfish in a breeding tank with a sponge filter. These types of filters don’t produce much of a current except for bubbles at the surface.


5. Increased Chasing Behavior from Males

Chasing is a normal part of spawning behavior in goldfish, and it is part of a goldfish mating ritual. Male goldfish specifically will chase female goldfish around the tank, usually nudging underneath her tail fin or her belly. This is common during spawning season when male goldfish pick up when a female is ready to spawn. It can either encourage an already pregnant female goldfish to release eggs, or it can indicate the female is going to be pregnant soon.

If this behavior becomes persistent or goes on for hours, it can be quite stressful for the female goldfish. If this is the case, you might need to separate your goldfish for a short time to allow the female goldfish to recover. It is also a good idea to have more female goldfish in the tank than males. This allows some of the female goldfish to catch a break so that they aren’t constantly being chased by the males.

nymph goldfish in the tank
Image Credit: Chaikom, Shutterstock

6. Appetite Changes

When a pregnant goldfish is about to deposit her eggs, you will notice a change in her appetite. She may refuse food and become quite sluggish. A male goldfish may also be chasing and nudging at her belly to encourage her to deposit eggs. This means that she is ready to deposit her eggs and she is finding a comfortable place to spawn. If the conditions are not right, this process can take longer.

If you aren’t entirely sure that your goldfish is pregnant, yet they are refusing food, it could be for several environmental or health-related reasons.goldfish divider

Conclusion

If you are a goldfish breeder or hobbyist, it can be exciting to find out that your goldfish is pregnant. By knowing these signs, you can also use them for future reference to determine whether your goldfish could be pregnant or not. If the spawning conditions are ideal and you have a mature female and male goldfish, the female is bound to get pregnant at some point. Since goldfish breeding isn’t always easy, you might need to perfect their living conditions before you notice spawning behavior.

 

Featured Image Credit: HORVITZ PHOTOZ, Shutterstock

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