Image Credit: Ho-Wen Chen (Creative Commons license)
A few years back, when my green glofish tetra was swimming sideways, I fed it cooked and skinned peas for a couple of days. But the fish died soon after. Only later I realized that peas aren’t really beneficial for insectivorous fish. I learned my lesson the hard way.
I was reminiscing about this awful incident a few days back and was inspired to educate new hobbyists on the subject. So, if you’re wondering, “why is my glofish swimming sideways?”, you’ve come to the right place!
Let’s begin.
Why Is My Glofish Swimming Sideways?
The most prevalent reason behind glofish swimming sideways is swim bladder disease. A swim bladder is a gas-filled internal organ that helps bony fish like glofish maintain buoyancy. And when this bladder is impacted due to illness, injury, or any other abnormality, the fish will have a hard time maintaining its buoyancy – resorting to swimming erratically like sideways.
Unfortunately, swim bladder disease is more common than we might think.
Even worse, the reason behind it can be so ambiguous that the disease often proves fatal before you even have a chance to put your finger on it.
That being said, swim bladder disease isn’t always responsible for glofish swimming sideways. Gastrointestinal parasites and bacterial infections can be the guilty parties too.
I’ll touch on them below, but first, let’s get swim bladder disease out of our way.
What Is A Swim Bladder?

All 5 glofish species are bony fish. And all bony fish have a specialized organ called a swim bladder that helps maintain the fish’s neutral buoyancy at its desired depth.
Oh, and it’s filled with oxygen and some other gasses.
You can think of a swim bladder as a diver’s buoyancy compensation device (BCD).
How Does A Swim Bladder Work?
Your glofish swiftly fills its swim bladder with oxygen by gulping air at the water’s surface. The gas then quickly passes through a pneumatic (air) duct to the bladder.
Next, the specialized gas gland that pulls gasses from the blood keeps the bladder filled.
Now, let’s look at what swim bladder disease is, its symptoms, and its causes.
What Is Swim Bladder Disease?
Swim bladder disease refers to a condition when a fish’s swim bladder is impacted due to injury, disease, abnormalities, or environmental factors. When the fish contracts this disease, it can’t hold air in the right areas – forcing the fish to swim on its side or upside down.
What Are The Symptoms Of Swim Bladder Disease?

Unfortunately, swimming sideways isn’t the only sign of swim bladder disease.
Due to distorted buoyancy, the fish may also sink to the bottom, float at the top, and float upside down. Basically, the fish will have tough luck maintaining its normal position.
The fish may also show physical signs like a curved back or a distended belly.
Even worse, the fish may experience difficulty eating or have no appetite at all.
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What Causes Swim Bladder Disease?
Swim bladder disease is caused by the compression of the swim bladder, which in turn is caused by overeating, constipation, rapid eating, gulping excessive air, and poor water quality. Dry flakes or freeze-dried food that expands when wet can also block the intestinal tract and impact the bladder.
Here’s a more detailed look into the causes:
Poor Water Quality
Poor water quality is often overlooked but the most common reason behind swim bladder disease. Consistent exposure to poor water parameters causes sudden and chronic stress in fish.
And stress interferes with regular homeostasis that negatively impacts the fish’s buoyancy.
So, if your glofish is swimming erratically, the first thing you should do is check the water parameters and correct them right away.
Wrong Feeding Style
Wrong feeding style here is an umbrella term for all the feeding and digestion-related complications that lead to swim bladder disease. It can be overeating, eating too fast, and eating the wrong food.
For instance, certain fish foods swell up when they come in contact with water. If the food expands in your glofish’s system, it can cause an enlarged stomach or block the intestinal tract, eventually disturbing the swim bladder.
You need to presoak these food items before offering them to your glofish.
Low Water Temperature
Low water temperature will slow the fish’s metabolism, which in turn slows the digestive process. This leads to enlargement of the gastrointestinal tract that puts pressure on the swim bladder.
The temperature requirements for each glofish species look different. For example, while glofish danios can thrive in somewhat colder water, glofish bettas are OG tropical fish that prefer warmer environments.
Here’s what temperature requirements for different glofish species look like:
- Glofish Tetras: 70-80 degrees F
- Glofish Barbs: 74-80 degrees F
- Glofish Danios: 65-77 degrees F
- Glofish Bettas: 78-80 degrees F
- Glofish Sharks: 75-81 degrees F
Secondary Complications
Sometimes, other organs become swollen and enlarged and affect the swim bladder. For instance, fatty deposits in the liver, cysts in the kidneys, and egg binding in female fish can affect the swim bladder.
A parasitic or bacterial infection can also cause the swim bladder to inflame.
Abnormality Or Injury
Complications like an inborn abnormality or an accident in the tank aren’t really within your control.
Sometimes, glofish are born with rare birth defects that impair their swim bladder. However, in these cases, signs are present from an early stage.
Other times, a hard blow from colliding into an object in the tank, a duel, or a fall can injure the swim bladder.
How To Treat Swim Bladder Disease?
The treatment for swim bladder disease depends on the cause behind it. If it’s due to digestive issues, fasting and feeding fibrous food can help. If congenital problems or injuries are behind it, you need to consult fish veterinarians.
But whatever you do, don’t tie foreign structures to the fish’s body. It can have devastating effects on the fish’s skin and mucus production. Any kind of external device doesn’t provide a long-term cure.
Here’s a detailed look into what you can do to treat swim bladder disease:
If It’s Due To Digestive Problems:
Increase the temperature slightly by a couple of degrees for the entirety of the treatment.
Fast the fish for 3-4 days. Fasting will most likely sort out whatever metabolism issue your fish has.
If your fish has an inclination towards a plant-based diet, feed boiled and skinned peas to break the fast. But if your fish is an insectivore, brine shrimp or daphnia work the best.
If It’s Due To Infections:
- Elevate the temperature slightly throughout the treatment.
- Then, treat the fish with a broad-spectrum antibiotic prescribed by the veterinarian.
And lastly, here are some other supportive treatment options irrespective of the cause:
- Keeping the water clean at all times
- Adding a small dose of aquarium salt to the water
- Reducing water flow to lessen the currents
- If a specific body part becomes consistently exposed to air, apply a stress coat to the exposed areas to prevent sores
- You may need to hand-feed the fish if it’s unable to eat on its own
- If the problem persists even after trying everything, consult an aquatic veterinarian and make arrangements for x-rays to evaluate the swim bladder.
How To Prevent Swim Bladder Disease?
Sadly, swim bladder disease can be challenging to detect and may have no permanent solution.
Check the water parameters as soon as the fish shows the first signs of disbalance. Although it may seem far-fetched, regular water changes and keeping the tank clean go a long way to prevent swim bladder disease.
You can also increase the water temperature by a few degrees if you suspect anything fishy. If it’s anything related to digestive complications, a warm environment will be beneficial.
Be mindful about what goes inside your glofish’s stomach. Always feed high-quality food made with healthy ingredients. And don’t forget to soak dried foods and thaw frozen foods first.
I think I have covered pretty much everything there’s to know about swim bladder disease in glofish.
Now, let’s look at the other two potential causes behind your glofish swimming sideways before I wrap this article.
Is Your Glofish Swimming Sideways Due To Gastrointestinal Parasites?
The most obvious sign of gastrointestinal parasites in glofish is their tendency to swim sideways. That’s because the fish will retract one of its fins, which will impact agility and stability in the water.
Besides swimming sideways, some other symptoms of gastrointestinal parasites are:
- Lethargy
- White marks on the skin
- Loss of appetite
- Clamped fins
- Scratching against different surfaces
To treat this condition, your fish needs to be put under a strict deworming treatment by the vet in a ‘fish hospital.’ Sorry but this is not exactly something that can be cured with DIY techniques.
Is Your Glofish Swimming Sideways Due To Bacterial Infections?
Some bacterial infections can also force glofish to swim on its side. However, this symptom is only present when the bacterial disease has progressed to an advanced stage.
Some common signs of bacterial infections in glofish are:
- Cloudy eyes
- Tattered fins
- Open sores
- Bloody patches
- White film on the body
The most effective treatment for bacterial infections in fish is antibiotics. However, you need to discuss with a fish vet before starting any treatment.
Final Words: Why Is My Glofish Swimming Sideways?
Glofish are as hardy as they come. However, if you often catch your glofish swimming sideways, it’s a telltale sign that something’s wrong with the fish.
In 9 out of 10 cases, the reason behind a glofish swimming sideways is swim bladder disease. This condition can be caused by an injury, an inborn abnormality, digestive complications, or stress factors.
Irrespective of what the pretext is, this disease will cause your glofish to swim sideways, as well as sink to the bottom or float to the top involuntarily.
All in all, life will really be miserable for your fish.
Depending on the reason behind swim bladder disease, several treatment options are available. You would want to get in touch with a local vet specializing in fish before starting any treatment.
And lastly, gastrointestinal parasites and bacterial infections can also cause your fish to swim sideways. So don’t forget to look into them as well!
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