Goldfish Swimming on its Side: Causes + What to Do

Goldfish are quite resilient fish. They can hold their own in poor living conditions and come out healthy and thriving. However, with age and other issues, they tend to get sick and may be observed to swim on their sides.

Goldfish may swim on its due to a swim bladder disorder, old age, overfeeding, or sleep. Swelling of the swim bladder, caused by gas buildup, is the most typical cause of this behavior in goldfish. Other causes include poor water temperatures, illnesses, and constipation.

Besides these causes, your goldfish could be dead (it’s sad, I know), and the movements of the water make it look like it’s swimming on its side. If it stays motionless for more than 6 hours, check on it.

Goldfish Swimming on its Side

Why is my goldfish swimming on its side?

Goldfish can float on the side, whether normal or sick, depending on the situation. However, it is crucial to be on the lookout for potentially stressful conditions to avoid making assumptions when the goldfish may be in trouble. Here are some common causes:

Causes of Sideways SwimmingWhat to Do
Swim bladder disorderTreat with medication
Poor water qualityChange the water regularly
Unfavorable water pHAdjust pH to 7-8.4
Unfavorable water hardnessAdjust hardness to 10-20 dGH
Incorrect water temperature Adjust temperature to 68-74°F
Stress Introduce plants and avoid aggression
Diseases and parasitesTreat them with drugs
Sleep Leave the fish alone
ConstipationTreat the swim bladder disease and avoid overfeeding

1. Swim bladder disorder

It is common for intestinal parasites like worms and other pathogens in the gut to induce swim bladder disorder. However, the most common and recognized causes of the illness include overfeeding, feeding too quickly, or inhaling too much air while feeding.

The most fundamental principle of a swim bladder problem is that if it is emptied, the fish will fall to the bottom because it lacks buoyancy. Inversely, the fish will come to the top if the bladder is filled with gasses.

Because a swim bladder infection interferes with the fish’s equilibrium in the water, the floating fish will most likely lie on its side at the surface.

If the fish gets a swim bladder infection, it will have difficulty staying upright in the water. To ensure that the fish is still alive, look for evidence of movement and breathing. Otherwise, if the fish remains immobile with no signs of breathing, it is most certainly dead.

2. Constipation

If the goldfish is constipated, it is more prone to developing a gas buildup, resulting in a swim bladder infection, the same as if the fish is overfed.

3. Constipation

Constipation is caused by the fish gulping down granules that usually swell up like sponges as they draw up water from the fish’s mouth and the other parts of the digestive tract.

When enough force is exerted on the swim bladder by the gas from the inside, it will swell, and the goldfish will struggle to swim in an upright position.

4. Temperature

Low temperatures frequently hinder digestion in all animals. The same applies to goldfish. A goldfish can have difficulty digesting food, particularly proteins, if the temperature goes too low.

The inference is that the unprocessed food swallowed by the fish causes a gas build-up in the gut, resulting in a swim bladder disorder which makes the fish swim on its side.

If you’re keeping platies and goldfish together, ensure the temperatures stay within the overlapping range of 70-74°F. Platies prefer a slightly higher temperature than goldfish, but there’s an overlapping range where the two can stay together.

5. Advanced age

A younger goldfish will be more active than an older one. The older one prefers to rest more frequently, particularly near the tank’s bottom. A sleeping goldfish will probably lie on its side, and a close look will help establish whether it’s still alive or dead.

6. Underlying health conditions

Dropsy, fin rot, and columnaris are the most notorious conditions that can cause a fish to become so fragile and lifeless that it can only stay in one position, usually near or at the bottom of the tank.

7. Ich

A close inspection of the fish may reveal if the goldfish is scratching itself against the substrate. This habit is caused by a condition known as Ich, a parasite that attacks fish and affects their skin, causing an urge to scratch.

The only way for the goldfish to scratch its side in the aquarium is to swim to the bottom and rub the affected side on the substrate. 

Usually, the side it rubs the most is the one with the worst case of the infection. It’s a relatively unpleasant sensation for the goldfish, and it frequently causes spots to form on the fish scales.

It’s crucial to highlight that the ich can often be lethal if left untreated. Goldfish can naturally rid themselves of the parasite in the wild. The same is not true if they are in captivity.

8. Sleep

As previously said, if your goldfish is resting on its side but still breathing, it’s most likely asleep.

A goldfish is a relatively active fish. It will most likely get weary and seek refuge at the bottom of the tank, where it feels safest. Goldfish also require rest that they can only get while lying on the substrate.

9. Water change

Water changes in a pond or aquarium will most likely impact water quality (whether positively or negatively). A goldfish will distinguish the change in water quality and react accordingly.

It becomes stressed if the newly added water has poorer quality than the previous one. It will most likely rest on its side if the conditions are extremely unfavorable.

This can also occur due to the new tank syndrome if you introduce the fish into a new tank with a different water quality.

A pH of 7.0 to 8.4, hardness of 10 to 20 dGH, and water temperature of 68-74°F are ideal for keeping goldfish. It’s advisable to instal an aquarium water heater to maintain the temperature.

If these conditions are not met, the goldfish will be exposed to a stressful environment. You should also check the pH on a regular basis and eliminate nitrates and ammonia as soon as possible to guarantee that they are not present in the water.

10. It’s dead

Your beloved goldfish could be dead if it stays motionless on its side.

A dead fish typically floats because, as the body decomposes, the bacteria that consume the flesh release gases that rush to fill the body’s cavities. Because gases possess a lesser density than water, the fish will float.

As a result, it may be necessary to establish if the floating goldfish is still dead or alive. The symptoms to watch for include a curved back, a distended abdomen, and if the fish struggles to maintain an upright position.

What to do

If you feel your goldfish is having problems, you should check the water quality first. Always execute a water change if there is an issue with the water quality. A pH of 7.0 to 8.4, hardness of 10 to 20 dGH, and water temperature of 68-74° Fahrenheit are the most ideal conditions for the water.

It would also be prudent to introduce flora into the tank to eliminate the possibility of stress. Goldfish enjoy densely planted regions because the plants provide them with hiding places.

Plants also add oxygen to the water, especially on the day when photosynthesis is at its peak. The plants use up carbon dioxide and give out oxygen. The fish will not suffer oxygen deficiency in a planted tank.

If there are any inherent ailments, they should be treated too. Also, one of the most effective treatments for swim bladder disease is feeding the fish with peas.

Nevertheless, if a goldfish slays still on its side at the bottom, see whether it is asleep. Try and initiate some excitement by tapping on the tank to see whether or not the fish reacts.

After taking such action, you should identify potential difficulties and implement the best remedies correctly. If the goldfish are in a pond, ensure you keep the pond water clean to avoid diseases.


Goldfish have a lifespan of approximately 10 to 15 years. They become weaker and less active as they advance in age. Their sluggish nature and weakness will compel them to pause more regularly, either by lying on the substrate at the base or finding something to support themselves. 

They may grow weary more quickly and struggle to flap their fins on either side. As a result, they may use one-side flaps. They are also more vulnerable to illnesses, which can badly impair them and keep them immobile.

Always check their living conditions to help them stay healthy. If you can’t do these tasks, hire someone with the needed skills to do it for you.


Leave a Comment