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

Fishes can be your pet too as they are cute, adorable, vibrant, and active creatures that will bring such entertainment in your home.

There are fishes that are amazing to keep as pets, among these are Angelfish, Corydoras Catfish, Bettas, Plecostomus, and Swordtail.

Eventhough they are just a small creatures swimming around in your aquarium, having them as pets is easier said than done.

If you keep them as pets, they require the same level of care as any larger animal.

If their care protocols are not followed, they experience a variety of conditions.

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 as it is toxic to fishes when high level is reach.

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.

Fish placed inside chlorinated water may experience respiratory problems.

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.

It is best to maintain a certain level of chlorine in the water to keep fishes suffering from health issues.

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.

Ammonia is converted to nitrites, which are then converted 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 such as pellets 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.


Fishes are not realizing that they are overeating.

They tend to keep on eating without knowing their limit.

They are getting an upset stomach or constipation, when given too much food, specifically low-quality food,

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.


To proceed, it’s time to start treating the abnormal behavior now that you’ve gathered information about it.

Fish may swim in unusual ways for a variety of reasons.

The good news is that, provided you can identify the issue, there is always a way for your fish to return to normal.

With proper research and diagnosis of the problem, your fish will be back to normal in no time.

It’s always a good idea to seek expert advice that can help you every step of the way.