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How to Cure Swim Bladder Disease in Molly Fish

Updated November 21, 2016

Fish swim bladder "disease" causes a fish to lose its buoyancy. You can identify a molly (Poecilia) with this so-called disease by observing how it is swimming. A fish with this disorder may float in a strange position, possibly vertically, on its side or upside down. You may notice that the molly is not able to swim to the top of the tank to eat food. A molly infected with swim bladder may not survive, despite treatment. There are several causes of swim bladder disease, but treatment is the same no matter what the cause. If successful, you will need to try to find the cause of the disorder and rectify it to avoid having it happen again.

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  1. Remove some water. Any time you notice that a fish in your aquarium is sick, do a partial water change. Siphon 25 per cent of the aquarium water into a bucket. Empty the bucket down a drain or outside.

  2. Add water. Use clean water to rinse out the bucket. Then proceed to add clean water back into the tank using the bucket. The tank should be filled to within 1 inch of the top.

  3. Add salt. Mollies should live in a brackish water environment. Brackish water has a higher content of salt than fresh water. Add 1/2 tsp of salt per gallon of water. A tank that had salt in it prior to the water change should receive 1 tsp of salt per gallon.

  4. Raise the temperature. Turn the aquarium heater up -16.7 degrees C.

  5. Peel the pea. Use a knife to peel the skin from the defrosted pea. Cut the pea into quarters.

  6. Feed the fish. Drop the pea into the water. Watch to make sure the sick molly gets to eat some of the pea. You may have to hold the pea close to the molly for it to get to eat.

  7. Remove any leftover pea from the aquarium water.

  8. Feed the affected molly fish a defrosted pea every day until the fish appears to be better.

  9. Tip

    Once the fish recovers from the swim bladder disorder, look for what caused the problem. It may be something complex, such as a bacteria, or something as simple as an injury. Swim bladder disease is not contagious. However, multiple fish can contract it from a water problem such as a bacterial build-up in the water. A fish can live a long life with swim bladder disease. You will need to make accommodations for the fish to get food. Hand-feeding will enable the fish to eat daily.


    Due to the body shape of balloon mollies, they are at greater risk to develop swim bladder disease than mollies with regular-shaped bodies.

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Things You'll Need

  • Water siphon for aquarium
  • Bucket
  • Clean water
  • Salt
  • Frozen pea, thawed
  • Small kitchen knife

About the Author

Amy Shelleby
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