Fish Swimming Upside Down After Water Change – Why?

Fish are wondrous, gill-bearing organisms that belong to the aquatic group of animals. With the majority of freshwater and marine life overtaken by fish, they dominate water bodies.

Fish Swimming Upside Down After Water Change

However, various species of fish are also domesticated as pets for many years. Though, keeping them as a pet is easier said than done. Just like any animal larger in size, they require full care. They also become victims of various diseases if their care protocols are ignored.

Indications of fish facing distress are swimming erratically, upwards, upside down, gasping at the surface of the water, etc. Another signal that marks discomfort is their loss of appetite.

Upside Down Swimming

Fish can show symptoms of swimming upside down, right after a water change in their tank. There are various reasons they exhibit this behavior. Most of it occurs due to environmental issues, and some due to internal medical problems.

Reasons fish tend to swim upside down:

Excess Nitrates In Water

If a fish shows abnormal behavior, such as swimming upside down, it may be subjected to excess nitrate concentration. The water that fish swim in should contain a certain amount of minerals and chlorine.

Excess nitrate in the water can be a problem. If fish do not get nitrates according to requirement, it can hinder the process of osmoregulation.

Osmoregulation is their ability to regulate the pressure of the body fluids. If this process weakens, it can cause swelling of organs and malfunctioning of the swim bladder. This causes the fish to lose its sense of swimming usually, making it float frenziedly and uncontrollably.

Excess Chlorine In Water

If you are a fish owner, you must keep your fish tank dechlorinated. As mentioned before, any chemical and mineral misbalance in the water can prove harmful. Excess chlorine in the tank can cause burns to fish’s gills.

These organs are as sensitive as they are vital. Along with breathing issues, it also hinders osmoregulation and causes the fish to swim upside down uncontrollably.

Insufficient Water Conditioner

A water conditioner is used to purify the water tanks of chlorine and chloramines. It neutralizes the harmful effects that are usually caused by these elements. However, if there is no regulation of the amount of conditioner added to the tank, it can be problematic.

The slightest bit of chlorine or chloramine left in the water can trigger a detrimental effect. Aforementioned, imbalances of such sorts deter osmoregulation and cause swim disorders.

Unclean Water Tanks

Cleaning the water free of fish waste is as important as feeding the fish. It is wise to clean the water tank regularly. If these measures are not taken, the accumulating fish wastes form ammonia spikes.

The ammonia converts to nitrites, which then converts to nitrates. This causes an increase in the nitrate levels of the water, making osmoregulation difficult. As discussed before, we know the effects lack of osmoregulation has on the fish’s swim pattern.

Unstable Water Temperature

It is highly significant to maintain a specific water temperature, which ranges within normal. The fish’s metabolism directly depends on the temperature of the water. The lower the temperature, the slower the digestion process.

This can cause constipation and gastrointestinal tract enlargement in fish. This enlargement of the tract pushes against the swim bladder. An issue in the swim bladder makes the fish lose its buoyancy and causes it to float upside down.

It is recommended to keep the temperature of the water between 78-80 degrees Fahrenheit.

Bacterial Infection

If a fish acquires a bacterial infection in the water tank, it can show abnormal behavior. Any bacterial infection can directly affect the swim bladder. The swelling of the swim bladder does not allow the fish to regulate it properly.

This causes them to lose control of the steering or swimming mechanics. In situations like this, they tend to float around in the water without any sense of direction.

Expansion Of Food In Water

Certain kinds of food expand when they get moist. Examples of such foods include freeze-dried food and dry pellets. A fish that feeds on food like this is subjected to bloating. The bloating of the stomach also causes swim disorder.

The bloated stomach begins to push against the swim bladder, making it impossible to control and regulate. Hence, feeding fish with something that doesn’t cause bloating is an excellent measure to prevent buoyancy loss.

Floating Food In Water

A fish that feeds on food that floats on top of the water has an increased chance of intaking air. When they intake too much air, the chances are that some of the air goes into the swim bladder. Excess air in the swim bladder violates the balance, causing the same issue with buoyancy.


Fish don’t realize when they overeat. They tend to keep on eating without knowing their limit. Hence, when they feed too much food, specifically low-quality food, they get an upset stomach or constipation.

Constipation causes a blockage in the digestive process and makes them lose the regulation of their swim bladder. This disorder again brings the same issue to light, with the fish losing direction of swimming.

Therefore, it is advised to feed the fish amounts that it can easily digest. Also, it’s wiser to provide them the best quality of food one can manage.


What are you still doing here? Now that you’ve collected information regarding the abnormal behavior, it’s best to follow through with the treatment. Various reasons may cause fish to swim in unusual manners.

However, there is always a way for things to go back to normal. With proper research and diagnosis of the issue, it takes no time for your fish to go back to normal.

It is always wise to get expert advice that can guide you every step of the way.