Goldfish float if they are suffering from swim bladder disorder. A deformed or dysfunctional swim bladder, improper diet, and bacterial infections due to unhygienic water conditions cause swim bladder disorder. Also, excess air in the swim bladder affects buoyancy and makes the goldfish float.
Let’s talk about this in detail now.
How Swim Bladder Disorder Affects The Movement Of Goldfish?
The swim bladder is a vital organ that regulates the movement in fish. It keeps the fish buoyant by trapping air.
Thus, it helps the fish regulate its motion and swim at the desired depth. It also helps them stay upright.
The below image shows the anatomy of a fish. You can clearly see how the swim bladder looks like and where it’s located.

When the swim bladder loses its intended shape, the ability of the fish to control its movement is compromised.
Given below are the most common causes of the swim bladder disorder.
1. Deformed or dysfunctional swim bladder.
Your goldfish may be born with a deformed or dysfunctional swim bladder. This condition is common in fancy goldfish.
Although you may not notice it in the fish when it is young, the problems will be evident once it’s an adult.
If the swim bladder is too small, fish struggle to swim upwards. It will spend most of its time at the base of the tank.
Meanwhile, large swim bladders cause the fish to float at the top of the tank.
In either case, your goldfish may need surgery to rectify this condition.
Your veterinarian may prescribe radiographs or X-rays and plan the surgery after studying the issue.
2. Improper feeding.
Goldfish are voracious eaters. While gulping down food, they tend to suck in extra air, which increases the volume of their swim bladder.
Consequently, the fish start floating and have difficulty controlling their movement.
A low-quality diet can also cause gas formation in goldfish.
If you feed it freeze-dried or flake food without soaking it first, the food can expand in its digestive system and cause gas.
This gas will cause the fish to lose its balance. Unsuitable items like bread can also trigger this condition.
Fortunately, the normal movement gets restored once your fish releases this gas.
3. Infections of the swim bladder.
Dirty water and poor hygiene conditions trigger swim bladder diseases. Goldfish quickly dirty the water in their tank.
If you do not perform regular water changes or your tank filter is not efficient, the water quality will deteriorate over time.
An unclean tank is a breeding ground for harmful parasites and bacteria.
These germs will cause health problems, including infections of the swim bladder.
When the swim bladder is infected, it can result in mobility issues.
How To Cure Swim Bladder Disorder In Goldfish?
Congenital swim bladder conditions are beyond your control, and only a veterinarian can help with it.
However, most of the other reasons are avoidable.
Bacterial and parasitic infections occur when the water is dirty.
Invest in a good filter and perform regular water changes to prevent these infections.
You should also remember to remove any uneaten food from the tank to prevent it from causing issues to your fish.
Now, should your fish catch an infection, it will need prompt attention.
Not only will these infections cause swim bladder disorder, but they can also cause various other health conditions.
Another thing you can do is improve the diet of your fish.
Keep them on a neutral buoyant diet to avoid swim bladder disorder.
Feed sinking pellets to your goldfish as they prevent the fish from sucking air from the surface during feeding.
A fiber-rich diet will also be very helpful.
If you see your goldfish floating around after a meal, you can help them overcome this condition by feeding cut and blanched peas.
The fiber in the pea will push the gas from their insides and make them feel better.
Apart from diet modifications, also look at the temperature of the tank. Low temperature impedes digestion.
It can result in blocked intestines, which result in pressure on the swim bladder and affect the movement of the fish.
Now, if none of these steps help, it is most likely a permanent or genetic condition.
In such situations, surgical remedies may be necessary. Check with your veterinarian for the right course of treatment.
Why Do Goldfish Float Upside-Down Or On Their Back?
Swim bladder disorders can manifest in different ways.
It can cause fish to float in different directions and sometimes sink, float, or roll over.
Two conditions make goldfish swim upside-down or on their back:
- Swim bladder disorder, or
- Death.
It is highly unlikely that your goldfish will start floating upside down one fine day.
When this happens, the swim bladder must have been impacted for a while.
Most fish start by floating sideways or with their nose-down and end up floating upside down.
By the time your goldfish is floating upside-down, its swim bladder would have been significantly impacted.
It could be caused by an infection, consistently poor quality diet, injury, or significant swim bladder impairment.
Now, goldfish will also end up floating upside down when they are dead.
The fish will be still and will most probably show signs of decomposition if it is dead.
You can identify if a goldfish is dead by observing its eyes and checking for movement.
A live goldfish that is floating upside down will wriggle its fins and show other visible signs of life.
Why Do Goldfish Float On Their Side?
Swim bladder disorder can make a goldfish float on its side.
The good news is that if you notice your fish floating this way, you may be able to help it recover.
Treat it promptly, and it should get alright.
The first step is to adjust the diet and clean the water.
If it doesn’t help, consider administering anti-bacterial treatment or contacting a vet for a proper diagnosis.
Why Do Goldfish Float To The Top?
A goldfish may float to the top when its swim bladder is filled with gas or air, and the goldfish is not able to expel it.
If the goldfish is constipated, the intestine will press on the swim bladder and cause this problem.
It can also occur if the fish gulps down too much air or eats leftover food. The food may expand in its stomach and produce gas.
To help the fish overcome this condition, feed it fiber-rich food like cooked peas.
The peas will help it expel the trapped air and regain control over its movement.
Why Do Goldfish Float At The Bottom Of The Tank?
While bloated swim bladders make the goldfish float to the top, too small swim bladders make the fish sink to the bottom.
This condition is commonly observed in fancy goldfish that are overbred and prone to congenital health issues.
When your fish is unable to pull itself to the surface of the water, it is usually because the swim bladder isn’t the right size for its body.
It does not expand enough to push the fish up. Hence, it stays at the bottom of the tank.
Your goldfish will most likely need a surgical procedure to overcome this condition.
The vet will usually use an external floating attachment to help the fish move properly.
Why Do Goldfish Float After Eating?
Goldfish are constantly on the lookout for food and eat ravenously when they find it.
Now, when they eat, they gulp down air with food. This air reaches the swim bladder and increases its volume.
When this happens, the fish begin to float to the surface.
The same condition happens when goldish overfeed or eat wet food that expands in their stomach and causes gas.
Overfeeding causes the digestive system to push on the swim bladder.
This affects the buoyancy of the fish, and it ends up floating all over the place.
The goldfish will regain control over its movement after it releases excess air.
However, if this problem bothers your fish consistently, you should evaluate your feeding pattern and choice of processed food.
Sinking pellets and fibrous food will help with the condition to a significant extent.
Why Do Goldfish Float When They Die?
A goldfish stays afloat in water because of the air in its swim bladder.
This organ prevents it from rolling over and sinking in the water. It also helps the fish to stay at a desired height in the water.
When a goldfish dies, the buoyancy of the swim bladder takes over.
If it contains air, the goldfish will roll over and float to the top of the tank.
However, if there is no air in its swim bladder, it will sink to the bottom and begin to decompose.
During decomposition, the digestive system of the fish releases gases.
These gases fill up the internal cavity and push the fish upwards. Hence, it ends up floating upside down in the tank.