Why is Guppy Swimming Vertically? All You Need to Know

Guppies (Poecilia reticulata) are a common sight in most freshwater aquariums.

A peaceful species native to South America, there are over 300 varieties of guppy in different colors, sizes, and tail shapes. 

Also known as the million fish because of their breeding speed, guppies are likely to be the most active inhabitants of your tank, constantly swimming around in a playful mood.

However, if you find a guppy swimming vertically or upside down, stop to take a closer look.

It has most likely got a swim bladder disease (SBD), which can be fatal if not treated on time. 

What Is Swim Bladder Disease and How to Treat It?

As the name suggests, the condition affects the swim bladder – a gas-filled sac that helps a fish maintain its buoyancy. 

Caused by unsuitable food habits, injury, environmental changes like a sudden difference in water temperature, etc., SBD affects a fish’s ability to float or swim properly. 

It’s not an illness in itself but a collection of symptoms caused by other underlying afflictions. 

Let’s take a look at the common factors behind the condition and ways to tackle them.

Swim bladder in guppies

Unhealthy Feeding Patterns

Fish display varying levels of impulse control when it comes to eating habits.

In most cases, they’ll munch till supplies are exhausted. This is why you’ve to regulate the portions you feed them.

Excess feeding can lead to constipation and bloated stomachs in fish. A bloated stomach can press against their swim bladder, affecting their buoyancy.

This is when they’re found to be swimming vertically.

You’ll know whether a fish is constipated by observing when it poops. If the stool hangs for some time before falling, chances are your guppy is constipated. 

While some aquarists prefer starving their fish in such cases, others choose to feed them fiber-rich foods that aid bowel movement.

Here’s how you can use peas as a laxative to treat a guppy with SBD:

  • Thaw and boil a single, frozen pea
  • Peel the skin and soak it in water (this keeps peas from swelling inside guppies guts)
  • Feed the cooked  pea to the fish
  • Don’t feed the fish for the next 24 hours and wait for the pea to work its magic

Parasitic and Bacterial Infections

Swim bladder disease can also be caused by bacterial infection. This results in the guppy’s bladder filling with fluid, and the fish swimming upside down.

Diagnosing a bacterial infection involves an ultrasound followed by a pneumocentesis (sticking a needle into the guppy’s bladder to extract the fluid and test it to identify the errant bacteria). 

Once the cause is identified, proper antibiotic treatment can eliminate it.

Guppy fish in aquarium

On the other hand, parasites are typically common in aquariums and do not pose a danger to a guppy unless there are a large number of them in the guppy’s stomach. 

Camallanus is one of the more common parasites found in guppies. Brown or orange, they grow up to 0.8 inches and stick out of a guppy anus, wriggling like worms.

Irrespective of whether they are caused by bacteria or parasites, these infections need to be cured with antibiotics. So you must take the ailing fish to a vet for a checkup and proper medication.


Physical confrontations among guppies and other inhabitants of your fish tank can cause injuries to the swim bladder, too. 

Guppy fish are peaceful creatures who won’t retaliate even if they’re attacked. Hence it’s important to choose the right aquarium mates for these beautiful fish.

Guppy and Molly fish in an aquarium
Guppy and Molly fish in an aquarium

In case a guppy’s swim bladder is affected due to an injury, isolate the fish in a separate tank and allow it to recover in peace.

Also, make sure your tank is not overcrowded. Space constraints can cause fish to become territorial and display aggressive behavior.

Environmental Changes

Any alterations to their usual habitat can cause a guppy to go into shock and swim upside down.

Some common shock-inducing factors include:

You’re likely to notice a change in their feeding pattern if your guppy is stressed.

The fish will either be overeating or starving itself, having a bloated stomach, and/or swimming vertically – all indicative of SBD. 

To help the fish recover from the stress and relax, you should switch aquarium lights off, creating a dark, relaxing atmosphere. Also, try to eliminate any noise sources and other distractions to encourage the fish to rest and calm themselves.

Breeding Errors and Genetic Deformities

Sometimes, the attempts to breed prettier, more colorful varieties of guppies can lead to deformities in the fish.

Their organs, including the swim bladder, can be affected in the process. The problem isn’t evident from the start, making it a cause for concern.

Some guppies with deformed swim bladders may present with odd curvatures of the spine or abnormally shaped stomachs. 

In other cases, seemingly healthy fish might be predisposed to SBD due to underlying genetic conditions.

Such guppies require delicate handling and must be housed separately from other healthy, robust fish.

They also need to be on a fiber-rich diet and have a closely monitored feeding schedule. 

Ways to Prevent Swim Bladder Disease in Guppy Fish

Diagnosed on time, SBD is fairly easy to cure. But, easier than that is to take preventive measures. 

Healthy Feeding Patterns

Make sure you don’t overfeed your guppies. The ideal guppy portion size should be consumed in 2-3 minutes. 

Veteran aquarists have the following recommendations about feeding guppies: 

  • Ensure the food is fresh and of good quality to avoid digestion issues and constipation
  • Avoid using flakes or pellets that float at the top of the tank
  • Soak dried food before feeding to make sure it doesn’t swell in the stomach
  • Thaw frozen food before putting it in the tank
  • Use food that sinks to prevent guppies from floating at the surface and gulping air

Tank Maintenance

Poorly maintained tanks are one of the major contributing factors – not only behind SBD but also several other diseases.

So it’s crucial to maintain a clean tank with the right water and nutrient levels. Here are a few pointers to maintain an ideal aquarium for guppies:

  • Ensure regular water changes
  • Thoroughly clean your aquarium and add water before introducing guppies
  • If you plan to use tap water, add in some water conditioner to remove heavy metals, chlorine, and chloramines
  • Frequently check the water quality to keep your tank free of ammonia and nitrites, and arrest nitrates between 20 to 40 parts per million (ppm)
  • You can also add live plants to help stabilize nitrate and ammonia levels
  • Ideally maintain pH levels between 7 and 8
  • Guppies thrive in the temperature range of 75-78°F (24-26°C). Lower water temperatures make the fish sick, while higher ones lower dissolved oxygen levels leading to asphyxia
  • You can also add a dash of aquarium salt in the water for good measure

The Right Tankmates

As mentioned earlier, guppies are a largely peaceful fish species.

However, guppies in a male-only tank might display some aggression towards others in an attempt to establish dominance.

Introducing a few females and maintaining a balanced gender distribution is usually enough to address this.

While choosing tank mates for guppies, opt for other gentle species like:

These fish also prefer the same water conditions as guppies, thus reducing your work of maintaining temperature, pH, nitrate, and ammonia levels.

You should steer clear of housing aggressive fish in the same tank as guppies, particularly the following species:

Euthanasia and Isolation

Guppies with birth deformities or genetic diseases are difficult to treat. They require constant monitoring and care, which might prove to be impractical and stressful in the long run.

In such situations, your best bet is to euthanize the fish. If that seems difficult, you can isolate the affected fish in a separate tank and prevent them from breeding. 

In this way, their poor genes don’t propagate further and keep the healthy lineage intact.

We know you love your fish. That’s why you’ve to be strict with their feeding schedule and hygiene levels. 

It’s crucial that you –

  • Avoid overfeeding at all costs
  • Make sure you get a water change every week
  • Test the water quality frequently If you want, you can add some ammonia and aquarium salt to promote fish health
  • Ensure your fish are not exposed to extreme temperatures.

You can also check out our blog on how to care for a guppy to get a well-rounded idea about what to keep in mind while housing these lively, colorful fish in your home aquarium.

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