Swordtail fish swimming upside down – Why? How to fix?

Watching your fish swim upside down is the most bizarre scene that an amateur fish keeper can witness. In case your swordtail fish is doing so, you need to learn all about this issue and how to cure it.

So, why is your swordtail fish swimming upside down? This is probably because of swim bladder disease which can be fixed by not feeding the fish for three days and by raising the tank’s temperature to 80 degrees Fahrenheit. There are other causes which also include organ compression, infection, and constipation.

This article will go through all possibilities of fish swimming upside down and how to cure them.

Fix an upside-down (Swim bladder) – Video

Swim Bladder Disease

When it comes to swim bladder disorder, you must know that it is more like a disorder and less likely to be called a disease. This refers to a situation when the swim bladder is not functioning well. The first symptom is that your swordtail fish would be floating upside down or swimming at the lower levels of the water tank.

Such an issue should be treated instantaneously as a delay can complicate things, making it challenging for the fish to recover in time. The physical symptoms also include sinking to the bottom or feeling troubled to swim in an upright position. You may also notice slight changes in the body of your fish.

Therefore, it is vital for you to keep examining the fish physically to detect whenever there is any variation in the body. Your swordtail fish might seem to be uncomfortable and it might also show a distended belly. In addition, a curved back is usually listed as a symptom as well.

When you focus on the behavior of swordtails, you may or may not notice any change in the diet of the fish. Sometimes, they do not show any change but other times you can notice a drop in their usual appetite which indicates illness.

There could be numerous reasons that result into such an ailment of your swordtail fish. Eating too quickly or overeating is the top reasons which can only be effectively solved by not feeding the fish for three days.

On the fourth day, you can feed it soft peas. The right consistency of peas should be fed; neither too soft, nor too hard. Simply boil the frozen peas and squish out the inner substance from the pea skin and feed it to the fish.

For better results, raise the temperature of the tank between 70 to 80 degrees Fahrenheit so that the digestion is improved as cold water tends to slow down the digestive system.

Organ Compression

As mentioned above, this is another possibility that may also be a root cause behind the swordtail fish floating upside down. This is somewhat different from a swim bladder disorder as it is not directly linked with it.

This condition basically refers to a situation when the organs around the swim bladder are affected in a harmful way. The organ enlargement can cause the to press the bladder ensuing similar consequences. This can occur because of a cyst in the kidney or cysts in eggs in case of a female fish.

Fatty liver deposits and intestine enlargement can also be added to the list of common organ factors. These matters should be dealt with making immediate changes to the diet and surroundings. However, if you do not see any improvements, it is essential not to delay and reach out for consultation and treatment by a professional vet.


Other expected causes include infection. Your swordtail fish might be infected by parasites. This can happen if you have added new plants to the tank that carry parasites or if you have added new fish to the tank with the same infection.

Such infections can spread very quickly, damaging the entire tank in no time. In this case, proper care needs to be given to control and ultimately solve the problem.

Antibiotics prescribed by vets can also be given depending upon the severity of the situation. Moreover, you are advised to transfer the infected fish in a separate Q-tank where they would feel comfortable and safer. Usually, they fear and panic in crowded tanks as weakfish can end up becoming prey to the stronger fish in the tank.

Other causes

In addition to this, changes to the tanks like too much brightness or new lights can also be a reason for the discomfort to your fish making it swim at the bottom of the tank. You should also look out for any physical injury which might have impacted the ability to swim upright.


Learning how to prevent any disease is easy and actually the most important part of taking care of your swordtail or any other fish. As the proverb goes: Prevention is better than cure!

Here are some suggestions for fish owners who wish to prevent swordtail fish diseases like the swim bladder disease.

  • Give good quality food as a diet
  • Avoid overfeeding your fish
  • Occasionally add fiber-rich foods to the diet. Your main focus should be feeding them a balanced diet to maintain a healthy diet plan
  • Add healthy plants to the tank such as algae
  • Keep the water temperature between 70 to 80 degrees. Low temperature leads to slow digestion
  • Keep lighting of the tank to a medium
  • Quarantine all plants and fish before adding them to the tank
  • Avoid overcrowding the tank as stress can also lead to these issues
  • Regularly examine your fish in the tank to get hold of the problem right at the beginning

Related questions

Is swim bladder disorder contagious? Swim bladder disorder is not usually contagious, however; it depends on the cause behind it. If the problem occurs due to infections, then the bacteria can be contagious. Parasites, which are without a doubt highly contagious, are a lot of times the root cause behind swim bladder disease. Therefore, as soon as you diagnose an infection, make sure you transfer the infected fish in a separate tank till they are treated.

Can swimming upside down be fatal? This issue is not always fatal. If the problem is serious like the presence of swim bladder disorder, severe constipation, or organ compression, then it can prove to be life-threatening for the swordtail fish. However, there are all cases where the fish can live all its life years happily if they are treated right and on time. Delays in treatment are what usually cause severe problems.

How to feed fish during treatment? It is essential to feed a diet that can resolve most of the issues. It all depends on the right consistency of the food. Give a high-quality diet to permanently improve the health and immune system of your fish. If you are feeding peas for the treatment, boil them up and mash out the pea substance which is the main food for the fish. Also, if you are giving some other type of food, then soak it before you feed it to the fish. Hard food is a big no for ill fish. Feed your fish for only 3-5 minutes as over-eating can cause serious concerns.

How to maintain a healthy tank for swordtails? It is important to provide the fish with a clean environment. Use a cleaning kit for the tank. Test the pH, nitrite, and ammonia levels through a testing kit. Keep the water conditions accordingly. You can also try to add an appropriate amount of salt to the tank as it is good for fighting diseases.


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