Why is my Discus Fish Swimming on its Side?


Discus Fish Swimming on its Side

If your discus fish is swimming on its side, leaning to one side, tilting sideways or lying flat on the floor of your aquarium, you should know that there are problems. The behaviour mostly occurs at the dark corners of an aquarium, at the bottom or near the surface of your aquarium tank.

When your discus fish lies down or tilts to one side or the other, you should take that as a sign or symptom and not a disease. It can be a sign or symptom of many diseases or even stress.

Stress Caused by Improper Water Conditions

Discus fish are fragile and minor adjustments in the environment, particularly the water conditions are known to cause stress. The water parameters of your aquarium store should be your main consideration when working to keep the fish healthy and beautiful because they are more sensitive to the change of water parameters like PH level, temperature, nitrite levels and ammonia.

The setup of an aquarium tank for discus fish is not an easy job. And after the aquarium tank is established, you will have to do regular water changes so that you can keep the aquarium healthy. The life of discus fish in aquarium tanks is very different from that in the wild because the tank is enclosed and the waste has nowhere to go.

Accumulation of waste may cause ammonia fluctuation. Ammonia may kill the fish and so, you have to maintain its level and that of nitrites at zero. Ensure that the water is clean.

When adding discus to a new aquarium tank, you will have to be extra careful. First, you will have to wait for the nitrogen cycle to be complete and avoid cycling the tank when the discus fish are present because they are unlikely to survive the process.

For the nitrogen cycle to be complete, wait for at least one month before introducing your new fish. During the time, it is advisable you do regular water changes because replacing the evaporated water will not be enough. Remove the wastewater and add fresh water. Change 40 percent of the water in your tank after every 5 days to be sure that your Discus is safe.

  • Stocking Capacity

You have to be careful when deciding on the number of discus fish to keep in your aquarium tank and the plants you need for the fish. Addition of many plants to the aquarium tank or a large number of fish will make the management of the tank condition hard. A high stock level will require you to perform partial water changes more often and observe the changes in water parameters carefully.

  • Chlorine-free water

As I stated above, the water conditions of your aquarium tank are important for the survival of your fish. You have to use dechlorinated water. Remember that most municipals add chlorine to the water they supply as a way of killing germs. The chlorine is dangerous and can kill your fish. You, therefore, have to buy a test kit to know whether the water you want to use contains it. The chlorine will age out if you allow the water to sit for a few days before adding it into your tank. The other option involves buying a dechlorinator from a pet store.

  • Water hardness

Discuses prefer hard water. If the water hardness is not appropriate, you have to adjust it to reduce the chances of stress. The best way to improve the water hardness is to add peat and driftwood. After the two are ready for use, add them to your water filter or to the tank directly. If you are using your aquarium tank for breeding purposes, then you will need slightly softer water to help with the development of eggs.

  • Water PH level

The wrong water PH might make your discus fish swim on the side. Even though it can be hard to maintain a constant water PH, you have to observe the level carefully to prevent sudden rises or falls. Maintain the PH level at around 6.5-7.0.  When it comes to the water PH, stability is vital. The standard PH level for discus fish is 7.0 but the fish will thrive in constant levels between 6.2 and 7.8. Maintain a stable PH and do not worry about its variation from the standard PH.

  • Water temperature

Very high water temperature can be a big problem in your aquarium tank and stress the fish. Normally, you should maintain the water temperature at around 28 degrees Celsius (82-86 degrees Fahrenheit).

Your discus fish might show signs of stress after transferring from the store to your aquarium tank. But if they start showing the behaviour of swimming sideways, you should know that water is the main cause.

Discus Plague Causes Sideways Swimming

Even though most aquarists believe that discus plaque disease does not exist, it is known to affect discus fish in aquariums. Unfortunately, the disease is not traceable and can easily spread to the other discus fish too. If you identify any form of colour change, loss of appetite or notice that the fish is swimming off-balance, lying on one side, it is likely suffering from the Discus Plaque. The disease is serious and you will have to transfer the affected fish to a separate aquarium tank.

Swim Bladder Disorder Causes Sideways Swimming

The swim bladder is a vulnerable organ in discus fish. The organ gets affected in many ways. If your fish develops swim bladder disorder, it will display various signs such as swimming sideways and buoyancy. Some other symptoms include arched back or swollen belly.

Fish develop swim bladder disorder if they overeat or eat the wrong food. Wrong food includes the dry food that expands immediately it enters the stomach of the fish. Even more, if the water temperature is very low, the digestion process of your fish will slow down and the fish will consume more than they can digest.

If swim bladder disease has made your fish to swim on its side, you will have to move them to a different tank, wait for 2-3 days and then feed them with frozen peas. After a short time, they will be healthy again.


Like other fish, your discus fish are likely to catch parasitic or bacterial infections. Gill flukes are one of the commonest parasitic infections. Other infections include cloudy eye infections, which result from very poor water conditions.

Even though the disease is not serious, you will have to do regular water changes and add aquarium salt to your aquarium tank to kill the harmful bacteria and parasites. You should follow that with anti-biotics to help the fish recover faster.

Another common infection that is likely to affect your discus fish is the Tail and Fin rot. To spot the infection, you just need to examine the fins and tails. If they have a ragged appearance, your fish are suffering. The infection is contagious and you have to deal with it immediately. To eliminate the problem, you just need to do regular water changes and use anti-biotic medicine to treat the fish.

Ich is the most dangerous infection. The parasitic infection forms small white spots on the entire body of a discus fish. It is highly contagious and to reduce the risk of spreading, you have to catch it earlier. If left untreated the disease will result in 100 percent mortality.

If you are not sure whether your fish have developed the ich, transfer any affected fish to a separate tank and lower the temperature to a suitable level while using chemicals to treat the condition. For the quarantine tank, do regular water changes and give anti-fungal treatments to the fish. Usually, any affected fish will not last for many days but preventing the spread of this disease is important.

Related Questions

Which is the right water condition for discus fish?

Discuses are more sensitive to the water quality changes and therefore consistency is more important. They do well in slightly acidic water conditions and a PH level between 5.5 and 6.5 is recommendable. In the wild, they are more tolerant of high PH levels than their counterparts are.

They also require higher water temperatures than their counterparts – between 86 and 90 degrees Fahrenheit. Proper filtration and regular water changes are important for the survival of this type of fish.

What are the compatible tank mates of discus fish?

A: It is hard to get an appropriate tank mates for your discus fish because of the high temperatures they need. Bleeding heart tetras and cardinal tetras are good companions because they are native to the parts discus fish inhabit in the wild.

German rams are also good companions if the aquarium tank offers adequate swimming space and enough hiding spaces to prevent aggressiveness. Remember to quarantine new fish before you move them to the communal aquarium tank to prevent the spread of diseases and illnesses.

Which is the appropriate tank space for my aquarium tank?

Discus fish are among the vividly coloured and beautiful tropical fish. Most aquarists believe that the fish species is more difficult to keep due to the need for pristine water conditions and a higher-quality diet. Caring for the fish can be a challenge because of the needed extra maintenance. The fish do better in shoals of five or more and will need adequate swimming space to remain healthy.

If you want a small aquarium tank, you should ensure that it has a 50 gallons capacity – experts recommend 75-gallon tanks. They also recommend undecorated tanks to reduce the chances of waste and debris collection. Discuses thrive better in heavily planted aquarium tanks.

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