Guppy Fish Swimming Vertically: Reasons & Solutions

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Quite frequently, I’ve noticed that my guppies swim vertically, consistently moving up and down. At first, I thought it was an innocent behavior. However, as I saw my guppy fish fail to survive afterward, I began researching that topic much more extensively.

Guppy fish swim vertically due to a swim bladder disease, secondary to an infection, injury, or sudden environmental changes. However, guppies may also swim up and down due to inappropriate water temperatures or careless feeding.

As we move forward, I will elaborate on how to identify the underlying cause for the condition and how to treat each case appropriately. I will also share a few tips to prevent this phenomenon from occurring in the first place.

Also Read: Guppies Diseases

Why Do Guppies Swim Up and Down?

Guppy fish shouldn’t swim vertically. For some species, this is an entirely natural way of moving. Shrimp fish, for instance, swim vertically (primarily for camouflage purposes). Other species swim this way because of feeding habits.

Yet, guppy fish are not known for manifesting such movements, at least not naturally. If your Guppies are swimming up and down, you can probably blame swim bladder disease. The swim bladder is an organ, a sack filled with gas that gives fish some control over their density.[1] 

Fish use it to maintain their balance in the water; it allows them to swim up and down. Because they use it to support their buoyancy, any harm suffered by the swim bladder will affect your fish’s ability to swim. However, this piece of knowledge doesn’t necessarily help you.

Understanding that your guppy has swim bladder disease won’t show you how to help it because it isn’t an actual disease. Instead, it is a symptom. To resolve it, you must identify the causes and elements responsible for harming the swim bladder.

You should know that swim bladder disease is just one factor among a few that can cause your guppy to swim vertically. You should take the time to rule out some of the other potential causes before treating your guppy for swim bladder disease:

Nevertheless, as swim bladder disease is the most common cause of a vertically swimming guppy, here are the possible causes and solutions for the conditions:

1. Inadequate Temperature

Water, whose temperature is lower than the ideal, can harm your guppy’s body. It will slow the digestive process, enlarging the gastrointestinal tract. This can exert pressure on the swim bladder, deforming it.

If an enlarged stomach or intestinal tract causes your guppy’s swimming disorders, you should start by raising the temperature (78-80 F).

The elevation in temperature is encouraged for a variety of causes of swim bladder diseases. You should also consider adding some aquarium salt.[2] If your fish refuses to recover, you should consider euthanasia. The damage to the swim bladder in some guppies is simply too severe to treat. You shouldn’t expect positive results in every single case.

The gastrointestinal tract is not the only organ that can affect the swim bladder. The other organs in the abdomen can also harm the swim bladder once they become enlarged.[3] For instance, the liver can accumulate fat deposits that could make it a threat to the swim bladder. The same goes for kidneys that have cysts.[4]

2. Injury

Physical confrontations between guppies and their tankmates can expose their swim bladders to injuries. The consequences and rate of recovery will depend on the extent of the damage. Some swim bladders might never heal.

If a physical injury is responsible for the swim bladder disease in your guppy, isolate it. Place it in a separate tank where it can recover in peace. Do not expose it to aggressive tankmates before it fully recovers. 

You should also avoid overcrowding (if this is an issue) by reducing the number of fish in your tank. The general rule of thumb would be one inch per gallon of water.[5] For example, if your guppy is 2 cm long, it should live in a 2-gallon tank. Two guppies will require 4 gallons and so on.

3. Infection (Worms & Bacteria)

Parasitic worms are typically not a cause for concern. They are reasonably commonplace in fish, and in ideal conditions, they are innocuous. However, a large and concentrated mass of worms in the stomach of a fish can create the kind of instability that will complicate its swimming behavior.

Also, bacterial infections could be so severe that they can compromise the functions of the swim bladder, debilitating the guppy’s ability to swim properly. A guppy whose bacterial infection has affected the way it floats should worry you. Such symptoms only manifest when the fish is seriously sick.

You should suspect an infection once you notice other symptoms rather the vertically swimming. You may also see white spots, rotten fins, and lethargic behavior. Your guppies may even begin to change their colors.

If your guppy has bacterial infections or worms, you should seek medical help. You can tackle parasites with antihelminthic medication. Bacterial infections, on the other hand, can be treated with antibiotics. However, you are still encouraged to consult a vet to ensure that you are applying the right medical solutions.

4. Environmental Changes

Guppies that are exposed to sudden changes in their environment can suffer from the sort of shock that can affect their swimming. Potential causes of trauma include a sudden spike or drop in temperature. You also see this in fish that have been introduced to new aquariums. 

The sudden transition from one tank to another can temporarily affect their swimming habits. If your guppy is swimming erratically as a result of abrupt changes in its environment, you need to treat the shock by eliminating the elements that have generated stress in the guppy. 

For instance, if the temperature is wrong, you should fix it by gradually raising or lowering it. To expedite the recovery process, you should switch the lights off. Make sure that you remove all distractions and sources of noise. This approach will encourage your guppies to rest.

5. Genetic Defects

One potential cause of your guppy’s swimming habits is genetics. Some fish are born with genetic anomalies. Their swim bladders could be deformed from birth. Such cases are often found among fish whose existence is the result of routine inbreeding. Unfortunately, you cannot help guppies whose swim bladders are naturally deformed.

If your guppy is swimming vertically because of a genetic deformity, euthanasia is your only course of action.[6] You cannot resolve this issue any other way. There is no way to rewrite your guppy’s DNA to eliminate this ailment.

However, you must prevent any further breeding to avoid defective offspring. If your guppy featured such behavior from birth, make sure to isolate it from the community tank. Hopefully, your healthy guppies will be able to overcome the issue.

6. Selective Breeding Errors

Attempts to improve the physical attributes of guppies through selecting breeding can produce deformities. In some cases, the guppies in question are not deformed from the start. Instead, they are more susceptible to illnesses that affect the swim bladder. These are also difficult to treat, though not impossible.

If selecting breeding has made your fish more susceptible to diseases that affect the swim bladder, your situation is problematic. You have no means of treating the guppy to make it less vulnerable to swim bladder disease. If the fish doesn’t have the ailment, your only tangible course of action is to prevent swim bladder disease from manifesting.

That means maintaining a pristine tank, eliminating dangerous tankmates, and providing a nutritious diet. But for some aquarists, keeping such vulnerable fish is too much work. Some of them prefer to remove vulnerable guppies altogether.

7. Inappropriate Food

If you give a fish bad or stale food, it will produce a lot of gas in the gut. This gas will enter the swim bladder, making the guppy excessively buoyant. A fish can produce similar results by gulping air as it hunts for food from the surface. This can also happen because of constipation or overfeeding.

In this case, stop feeding your guppies for three days. Once this period elapses, give them peas (cooked and skinned).[7] This approach works for fish with constipation. Regardless of your situation, you should consider it if your guppy is continuously swimming up and down.

Also Read: Why Is My Guppy Fat?

How to Prevent Your Guppies From Swimming Vertically?

While there are ways to treat guppies that are swimming vertically, you are better off taking steps to prevent them from developing such conditions in the first place, for instance:

1. Consider Euthanasia

You don’t have to kill guppies with genetic deformities. You can simply move them to a separate tank. Either way, the objective is to prevent them from breeding with healthy guppies and producing offspring with similar deformities.

As was mentioned above, that is particularly true if your guppies have presented the behavior from birth. Genetic disorders may manifest as your guppies grow (although they are likely to swim vertically at relatively young ages).

2. Choose the Right Tankmates

Violent confrontations in the tank can expose guppies to injuries that could compromise the health of their swim bladders. The most natural solution to this problem is to remove aggressive tankmates. Try to prioritize non-aggressive fish that are more likely to live peacefully with your guppies once you introduce them to the tank.

If you don’t have the option of removing aggressive fish and replacing them with peaceful species, you can add plants and decorative items to the tank.

They will give your guppies places to hide whenever they attract the ire of any bullies in the aquarium. If this doesn’t quell the violence, you can install a divider. Use it to separate the guppies from their enemies.

3. Feed Your Guppies Properly

Try not to overfeed your guppies. Give them food in quantities they can consume within two to three minutes. You should also pay close attention to the quality of the food. As was mentioned above, stale food is bad for their digestion. 

If you have chosen to give them dried foods, soak them beforehand. It is just as important to thaw frozen food before feeding it to your guppies. Some professionals will encourage you to use food that sinks. This will prevent your guppies from gulping air from the surface.

4. Maintain Hygiene

Try to maintain a clean tank, one that is free of toxins.[8] Install a filter and remove leftovers and dead organisms. You should also test for elements like ammonia, nitrates, and nitrites. Try to keep their concentrations at the ideal level. If they are not, replace the water more frequently.

A poorly maintained tank is going to expose your guppies to illnesses that will cause swim bladder disease. By maintaining a pristine environment, you are keeping these illnesses and infections away from your fish.

Regarding that topic, I highly recommend checking out the API Reef Master Test Kit (link to Marine Depot). By following the instructions, you will be able to tell the concentration of the toxins in your tank within minutes (including pH and ammonia).

5. Provide the Right Water Parameters

Try to maintain the appropriate parameters in your tank. This will encourage your guppies to thrive. The wrong pH and temperature will weaken their immune system, making them more susceptible to illnesses that affect the swim bladder.

Test the water whenever you notice suspicious behavior to ensure that your tank’s parameters are within the ideal range. In general, a guppy fish tank should feature these conditions:[9]

  • Water temperature: 72-82 °F (22-28 °C ) 
  • Water pH: 6.8-7.8 
  • Water hardness (dGH): 8-12 


Guppies typically swim up and down due to an underlying swim bladder disease. That situation can be reversible, such as in the case of an infection or appropriate water temperature. That is where your immediate intervention is mandatory.

Yet, guppy fish may also swim up and down due to genetic disorders. In these situations, you have little to offer. If you suspect that this is your case, you should isolate the sick fish, preventing it from breeding with healthy fish. Hopefully, you’ll be able to get rid of the problematic mutation.