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How to tell if a goldfish is pregnant

Updated February 21, 2017

Every now and then a goldfish purchased at a store will arrive pregnant. However, it can be hard to tell whether the goldfish is ready to lay eggs. There is specific treatment that female goldfish should receive if they are pregnant. It is important to keep track of the pregnancy to make sure that the babies will survive once they hatch from the eggs. It is also important to keep the mother away from the eggs after she has laid them. Pregnant goldfish should also be kept in isolation away from other fish of any kind.

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  1. Determine the sex of your goldfish. It can be very difficult to tell the sex of goldfish, but it is not impossible. Some varieties of goldfish are naturally fatter in the middle than others, which makes it even harder to tell if one is pregnant. Male goldfish will often have white tubercles on their gills. Females will often be slightly larger in size than males. Take your goldfish to the pet store where you bought it to have them verify the sex of the goldfish. You could also take the goldfish to a veterinarian who deals with fish. Once you have made sure that your fish is female, you can watch to see if she is pregnant.

  2. Prepare the tank for ideal egg-laying conditions. If you suspect your goldfish is pregnant you should be ready to care for the eggs. Use a large tank at least 20 gallons in size, and plant it with live foxtail and hornwort plants. These are ideal for goldfish to lay their eggs in. Make sure to have a water heater in the tank as well as an air stone. Feed the fish bloodworms to eat. Keep the water temperature around 21.1 degrees C.

  3. Keep watch over the next few weeks to see if the goldfish gets any bigger. If she does, she probably is carrying eggs. Make sure she is the only goldfish in the tank.

  4. After a few weeks, the goldfish should lay her eggs. Keep a close watch for this. If the goldfish remains in the tank after the eggs are laid, she will be likely to eat them.

  5. Separate the goldfish from the eggs. Place her in the other tank. Wait for the goldfish eggs to hatch. When they do, leave them in the spawning tank for several weeks as they grow stronger. Once the eggs hatch turn the water temperature down so the water is a little cooler. Baby goldfish can eat regular goldfish food, so just feed them once a day like the other fish.

  6. Tip

    If male and female goldfish are kept separate in different spawning tanks, they will likely be ready to mate after a few weeks. Place the fish together overnight and see what happens!


    It is easy to kill goldfish when they are in delicate circumstances, such as pregnancy. Make sure to treat them very gently.

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Things You'll Need

  • 2 20-gallon fish tanks
  • Air stone
  • Foxtail plants
  • Hornwort plants
  • Water heater
  • Bloodworms
  • Goldfish food

About the Author

Giselle Diamond is a freelance writer and has been writing since 1999. Diamond is experienced in writing in all genres and subjects, with distinguished experience in home and garden, culture and society, literature and psychology. Diamond has a Master of Arts in English and psychology from New York University. Diamond has articles published on both eHow and LiveStrong.

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