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Guppies Swimming at the Top of the Tank: Reasons & Solutions

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I’ve been growing guppies for years. They are among the first fish I ever got since they are hardy creatures and pretty easy to raise. However, there were times when I noticed that they spend too much time at the top of the tank. Since I got a little worried, I began researching pretty extensively why guppies swim at the surface.

Guppies tend to swim at the top sections of the tank due to oxygen deficiencies, mostly secondary to high water temperature, stagnant water, and toxin accumulation. That could also be a symptom of a swim bladder disease or stressful conditions, such as a stuffed tank and aggressive companions.

As we move forward, I’ll explain how to distinguish between an abnormality and natural behavior. That is because healthy and satisfied guppies also prefer the upper sections. If your guppies are indeed suffering, I will take you step-by-step on how to solve the issue.

Why do Guppies Swim at the Top of the Tank?

Guppies are fun to watch because they are active fish that swim all over the aquarium. But if your guppies are swimming at the top of the tank, you are probably concerned. After all, you expect fish to occupy either the middle or even the bottom of the tank. It doesn’t seem reasonable for fish to spend so much of their time at the top.

In truth, various breeds of fish are drawn to different parts of the tank. Some fish only swim at the bottom. Others swim in the middle. You also have fish that prefer to occupy the top half of the tank. Guppies are classified as top swimmers.[1] As such, their presence in the upper portions of your aquarium shouldn’t always concern you.

This behavior should only worry you in situations where your guppies are frequenting the upper sections and swimming at the surface of the water. You should also show some concern if you notice additional signs of trouble such as gasping, fading colors, and lethargy.

In such cases, you have every reason to worry. However, before we dive in, here is a table that summarizes all the possible reasons and solutions for top-swimming guppies:

Swim bladder syndrome – could be due to overfeeding, sudden pressure decrease, infectious diseases.Avoid feeding for three days, elevate the temperature to 80 degrees F, use cooked and skinned peas.
Poor water quality – the water parameters are not within the desired range (72-84 degrees F, pH between 7.0 and 7.2).Perform regular water exchanges, get a high-quality, stable heater device.
High ammonia, nitrates, and nitrites concentration – these are toxic to guppies and other fish in general.Check the water regularly with a testing kit, clean the water from leftovers and debris, perform more frequent water changes.
Direct oxygen deficiencies – that most commonly occurs due to stagnant water and a poor filter device.Replace a malfunctioning filter, or clean its sponge more frequently, consider using air stones.
Stress – stressful conditions may include stuffed tanks and bullying tankmates.Reduce the number of fish or decorations, consider moving aggressive fish to a different tank, or use an aquarium divider.
Lack of food – guppies, may swim upwards in anticipation of food when they are starved.Feed your guppies more frequently, pour the amount they consume within two minutes, consider an automatic feeder.

1. Swim Bladder Syndrome

Swim bladder disease is a prominent cause of erratic swimming behavior in fish. The swim bladder is a vital organ that allows fish to maintain their balance as they swim. If the organ is damaged by an injury or a disease or even compromised by environmental factors, such as a sudden pressure decrease, your guppy’s ability to swim appropriately will deteriorate.[2]

Some fish with swim bladder syndrome sink to the bottom of the aquarium – however, most fish float to the surface. If you observe a fish with this ailment, you will notice that it also struggles to remain upright. Some fish cannot stop swimming on their sides or upside down. If you look at their bodies, you will notice that their bellies are bloated.

2. Poor Water Quality

If your guppies do not have swim bladder disease, the water quality in their tank is probably to blame. Guppies require specific parameters to live healthy and happy lives. That includes a temperature ranging from 72 to 84 degrees F and a pH ranging from 7.0 to 7.2. The wrong pH and temperature will cause discomfort in your guppies. 

While they are hardy creatures that can survive small variations in their preferred parameters, there is a limit to what they can withstand. When pushed to the breaking point, some guppies might become lethargic, especially if they have contracted deadly diseases due to incorrect parameters. 

Other guppies may even fail to survive. You also have guppies that will rush to the surface as a way of escaping the pain. Because they are water-based creatures, they cannot escape the tank altogether. But that won’t stop them from swimming at the surface in the hopes of finding relief.

3. Ammonia, Nitrites, and Nitrates

Every aquarist has to deal with ammonia, nitrites, and nitrates. It is unavoidable, especially ammonia. Ammonia forms when waste products and leftovers in the water decay. On its own, the substance is toxic. But a high pH makes it even more toxic.

Ammonia, nitrates, and their mixtures are poisonous to guppies and can severely harm their fry.[3] It will make them sick before ultimately killing them. Nitrite, which is an ammonia byproduct, is also bad for guppies.[4] The same is true for nitrate, a nitrite byproduct.

Some guppies might rush to the surface as a way of attempting to escape the ammonia poisoning in the water. Other guppies might do the same because they cannot breathe. This is because ammonia can harm the gills, debilitating a guppy’s ability to breathe. Naturally, they are forced to swim at the top where the water has more oxygen.

Though, because the guppy’s gills are the problem, not the water, rushing to the surface won’t make much difference. Even high oxygen concentrations won’t suffice, and the sick will probably die if the conditions aren’t being solved. 

4. Direct Oxygen Deficiencies

An oxygen-deficient tank will force guppies to seek the oxygen-rich water at the surface. Oxygen enters the tank through the surface. As such, the water at the top always has more oxygen than the water at the bottom.

Oxygen deficiency has several causes. In some cases, the water has merely stagnated. This happens in tanks with no filters or aeration pumps. It can also happen in tanks whose filters and pumps are either malfunctioning or too weak to distribute the oxygen evenly to every corner of the tank.

On occasion, the temperature is at fault. The warmer the water, the less oxygen it can hold.[5] A heater can malfunction, causing temperatures in the tank to skyrocket. Your tank will suffer similar consequences if you live in extremely hot regions. Regardless of the reason, once the tank’s temperature rises, the oxygen levels will drop, forcing your guppies to look for sanctuary at the top.

If the temperature isn’t the problem, then overstocking might be the cause. Guppies are friendly fish that prefer to live in schools. But you shouldn’t have more guppies than your tank can accommodate. They will deplete the oxygen in the tank, leading to suffocation.

Where oxygen deficiency and ammonia poisoning are concerned, you should look for gasping and labored breathing in your guppies.[6] You will notice that they breathe heavily, opening and closing their mouths rapidly. If they cannot breathe, they will keep opening and closing their mouths.

5. Stress

Even though it is typically ignored, stress can compel your fish to frequent the tank’s top. You see this in guppies that were recently added to an aquarium. They will either hide or swim near the top because the transition was so shocking that they are desperately looking for an escape.

You might also observe similar behavior in your guppies shortly after you perform a water change.[7] If they haven’t acclimated to the water for any reason, especially if it has problematic substances like chlorine, they might swim at the top. Some people think that aggressive fish can force a guppy to seek solace at the top. 

You cannot always predict the behavior your fish will manifest in response to stressful stimuli. If guppies (which thrive in the company of peaceful fish) feel safer at the top of an aquarium filled with bullies, that is where they will run.

6. Lack of Food

Your guppies know that their food comes from the top of the tank. If they are starving, they will hang out at the top either in anticipation of more food or as a way of coercing you into feeding them. Like other pets, fish show their desires by acting in specific ways.

You may suspect that this is your case when your guppies swim at the top intentionally once you approach their tank. However, once being fed, they are less likely to stay near the water surface. They will naturally swim back down, turning back to their business.

Regarding misbehavior in guppies, here are a few related articles that you may also find useful. Each one features practical solutions you can take to improve the conditions of your guppies and their tankmates: 

How to Treat Guppies that Swim at the Top?

If your guppies are swimming at the top, observe them carefully. If they haven’t shown any signs of distress, you can leave them alone. A guppy isn’t necessarily in trouble only because it has chosen to act unpredictably.

On the other hand, if you have noticed signs of distress such as labored breathing, weight loss, lethargy, loss of appetite, and the like, you should take steps to identify why your guppies are swimming at the top. That will allow you to craft and deploy the right solution:

1. Ensure High Water Quality

To maintain optimal conditions in the tank, you must test the water regularly to ensure that the pH, temperature, and hardness are accurate. To achieve that, I highly recommend getting the API Reef Master Test Kit (link to Amazon). That is the precise bundle that I’ve been using for years with great success.

If the toxins levels are too high, you must carry out regular water changes. You should also remove all decomposing organic matter before it corrupts your water. Make an effort to test the water weekly and keep a close eye on the ammonia, nitrate, and nitrite levels.

You should also install a heater if you don’t have one. Otherwise, you will have a hard time maintaining a consistent temperature. Make sure that you check my recommendation for an aquarium heater. That device will keep your water temperature stable, preventing fluctuations that could harm your guppies’ health.

2. Improve Oxygenation

If your guppies are struggling to breathe and ammonia poisoning isn’t the cause, start by scooping water out of the tank with a clean jug and pouring it back. The water will collect oxygen as it splashes back into the tank, especially if you pour it back from a great height.

This act will also create a disturbance, increasing the rate at which oxygen dissolves into the water. Of course, you can’t do this every single time. It is merely an emergency solution. Inevitably, if you don’t have a proper-working filter, you should get one. I personally recommend the MarineLand Penguin Bio-Wheel Power Filter (link to Amazon).

If you already have a filter, find out whether or not it is working. If you conclude that it isn’t powerful enough to cause the sort of agitation required to distribute oxygen throughout the tank, get a more powerful filter, not to mention a better aeration pump.

For some people, it might be cheaper to add air stones to the tank. I personally use the Pawfly 1 Inch Air Stone (link to Amazon) bundle. That kit consists of ten pieces of air stones which you can quickly scatter across your aquarium. Within minutes, they will turbulent stagnant water, improving oxygenation dramatically.

Of course, none of these solutions matter if your tank is overstocked or if the temperature is too high. If necessary, reduce the number of guppies in the tank. Keep only those fish that the tank can accommodate. 

And if the temperature is the source of the reduced oxygen levels, you should take the necessary steps to remedy the issue. That may include taking the lid off the tank, keeping the aquarium away from direct sunlight, using a fan to blow across the surface, and adding ice cubes (in a zip-close bag).

3. Feed Your Guppies Properly

That goes without saying. If your guppy keeps swimming at the top because it wants food, feed it more. Keep in mind that guppies should be fed no more than two meals a day. If you have fed your guppy the appropriate amount and took the time to watch as it eats the food, don’t give it more.

Ideally, you should feed your guppies the amount of food they can consume within two minutes. Overfeeding your fish will lead to complications like constipation and swim bladder disease.[8] But that assumes that you actually saw the guppy eat the food. 

Don’t assume that your fish is well-fed simply because you sprinkled food in the tank. If you believe that the competition in the water is so stiff that one or more guppies rarely eat to their satisfaction, you can isolate them, remove the aggressive feeders in the tank, or squirt the food in the areas your guppies frequent.

If you keep forgetting feeding your guppies, I highly suggest considering getting an automatic feeder. I personally use the Eheim Automatic Feeding Unit (link to Amazon). This device allows me to go on vacation without worrying about my fish. Even when I’m home, the machine will back me up each time I forget to feed my beloved pets.  

4. Treat Swim Bladder Diseases

If you suspect that your guppy has swim bladder disease, don’t feed it for three days. During this period, you should raise the temperature to 80 degrees F.[9] If constipation is to blame for the disease, consider feeding your guppies peas. The peas should be cooked and skinned. 

Do this on the fourth day of fasting. Yet, this won’t work if an infection caused the swim bladder disease. That is why I suggest consulting a vet to prescribe an antibiotic if necessary. You should also consider adding some aquarium salt.

5. Mitigate Stress

If your guppies are stressed, remove the source of the anxiety. If bullies are the problem, you can either remove them or place a divider in the tank. Still, it might be easier to add plants and decorations. The guppy can use them to hide. Sometimes, it is necessary to place the tank in a place that doesn’t get that much human traffic. 

You are also discouraged from tapping on the walls of the tank. That can induce stress in your guppies. If your guppies have a clean tank with the appropriate parameters and suitable hiding places, stress is unlikely to manifest.


Guppies usually swim at the top of the tank because that is where they feel most comfortable. That is most commonly a natural occurrence, and if your guppy appears healthy, you don’t necessarily have to do anything about it. However, if your guppies also appear lethargic, swim differently, or change their color, they probably suffer. 

Then, you should identify the cause and treat it. I suggest starting by testing the water for toxins such as ammonia and nitrates. If they are within the appropriate range, move forward by testing the temperature and oxygenating system.