Why is my Discus Fish Swimming on its Side?

Freshwater fish like the discus can be a real challenge to keep. But the real issue for aquarists arises when your fish starts showing unusual behavior like swimming on its side.

But what exactly causes discus fish to swim on their side? The main reason why discus fish exhibit this behavior is because of either stress caused mostly by changes in water parameters or some sort of disease.

But the question remains, what kind of adjustments in the water or disease exactly causes this behavior? We will find these out in depth in the next few paragraphs.

Stress due to improper tank conditions

Temperature82-86 degrees Fahrenheit
Hardness1-4 dKH
Ammonia0 ppm
Nitrite0 ppm
NitrateLess than 20 ppm

We already discussed how discus fish are not a beginner’s pet, the main reason being their fragile nature. These fish can very easily accumulate stress from very minor adjustments in their environment, most of which comes from the water. Water parameters should be a priority for you when keeping these beautiful fish, as they are extremely sensitive to changing parameters such as temperature, pH, ammonia, and nitrite levels.

Discus fish are generally most comfortable in a water temperature of 82-86 degrees Fahrenheit. This combined with a pH of around 6-7 makes the perfect environment for their survival.

Now comes the important part; you should regularly check on ammonia levels in the tank water and make sure that they always remain zero.

This can easily be done with a weekly water change of at least 50%. If you don’t know how to check ammonia levels, you should get a cheap ammonia test kit from your local pet store.

Discus fish may show signs of stress when they move from the pet store to your tank, but if they start showing behavior like swimming sideways out of the blue, it is usually an indication that your water is causing them to display this sort of behavior.

Discus Plague causing sideways swimming

Although most aquarist don’t believe such a disease exists, Discus Plague can affect your fish. Unfortunately, it’s untreatable in most cases and can spread to other discus fish as well. If you notice any kind of color change, a loss of appetite, or see that your fish goes off and lays on its side or swims off balance, chances are it’s suffering from Discus Plague.

This is a very serious disease and even though it is mostly untreatable, you should still move the affected fish to another tank to avoid the spread of disease.

Keep doing frequent water changes and give anti-bacterial medication. This might increase its chances of survival, but still do not fully guarantee them.

Swim Bladder Disorder causing sideways swimming

Swim bladder in fish is a particularly vulnerable organ that can be affected in a number of ways. A discus fish that has a swim bladder disorder will often display buoyancy and swim sideways. Other symptoms can include a swollen belly or an arched back.

So, what causes a swim bladder disorder?

A fish can develop swim bladder disorders if it’s either overeating or eating the wrong foods. This means dry food which expands when it reaches the discus fish’s stomach. More so, if your water temperature is lower, the discus fish’s digestion process slows down and hence it eats more than it can digest.

If you find that a swim bladder disorder is causing the sideways swimming behavior in your fish, your best bet is to transfer them to a separate tank and after 2 or 3 days, feed them frozen peas and your fish will be healthy again in no time.

Infections in discus fish

Just like any other fish, the discus fish can just as easily catch a bacterial or parasitic infection. We covered Gill flukes earlier, which is also a kind of parasitic infection, but what other diseases like these can a discus fish get affected with?

One common infection is the Cloudy eye infection, the most probable cause of which is poor quality water. Although not very serious, you need to start doing regular water changes of atleast 50% along with adding aquarium salt to the tank. This should be followed by adding anti-biotics in the water to help your fish recover quickly.

Another infection that discus fish can catch is Fin and Tail rot. It can be spotted by examining your fish’s fins and tails which will give off a ragged look. This infection is contagious and hence, should be dealt with immediately. The easiest way to do this is to, once again, conduct regular water changes along with treating your fish with anti-biotic medicine.

Perhaps one of the most dangerous of all is the Ich. It’s a form of a parasite infection that causes small white spots to appear all over your fish’s body. The major problem with Ich is that it is highly contagious and needs to be identified as soon as possible in order to reduce the risk of spreading. And what’s more worrisome, is that the disease results in a 100% mortality if left untreated.

If you are certain that your fish has developed Ich, you should transfer the affected fish to a quarantine tank at once. In your main tank, lower the temperature to the higher end of the suitable range, while performing chemical treatments to contain the infection. In the quarantined tank, start doing regular water changes along with giving anti-fungal treatment to your fish. Usually, affected fish do not survive for long, but it’s extremely important that you avoid the spread of the infection to other fish.

Related questions

Why does my discus fish have black spots on its body? Discus fish camouflage themselves by making black spots appear on their body and it is not a sign of any disease.

How often do discus fish eat? For fish that are below the age of 12 months, you should feed them up to 5 times a day in small proportions. Fish over 12 months should be fed for up to 2 or 3 times in a day.

What should you feed discus fish? Discus fish are carnivorous and have a preference for foods like bloodworms and beef heart. Both frozen and live food work equally well.


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