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

Quite frequently, I noticed that my platies prefer the upper sections of the tank. At first, I gave credit to their personality. I thought that some fish merely prefer swimming at the top. However, the more I investigated the issue, I realized that the phenomenon could indicate a severe, underlying issue.

Platies typically swim at the top of the tank due to low oxygen concentrations, secondary to inappropriate temperatures, and stagnant water. However, platies may also sit at the top because of high ammonia levels, swim bladder disorder, underlying diseases, and food deficiencies.

As we move forward in this article, I will share a few tricks to prevent your platies from swimming at the top, taking care of inadequate tank conditions. Then, I will elaborate on a few cases that may also derive your platies swimming to the bottom sections.

Why is my Platy Sitting at the Top of the Tank?

Like most fish, platies do not always reveal to their owners that they are in distress.[1] They can’t talk, and they can sometimes maintain a healthy appearance even when they are sick. Therefore, you have to look for odd behavior that might point towards a problem in the tank.

One example of such behavior is platies that spend too much time at the top of the tank. In most cases, a fish will live a long and healthy life if you can maintain the quality of its environment. Fish only act out of the norm when the conditions in their water deteriorate.

While it isn’t always the case, if your platies are swimming at the top, you can probably blame a deficiency in their tank conditions. Some specific causes of this swimming pattern include:

1. Lack of Oxygen

Oxygen deficiencies are one of the most prominent causes of this behavior. Oxygen enters an aquarium through the top. As such, the top of a tank has more oxygen than any other section. If your tank doesn’t have enough oxygen to sustain its inhabitants, your platies will rush to the top because they need oxygen to live.

They will stay at the top until the situation below is resolved. Oxygen deficiencies have a variety of causes. One way of determining whether your tank is oxygen deficient is to look for gasping in your platies.[2] Fish that cannot breathe are always opening and closing their mouths. Like humans, fish gasp for air when they don’t have enough oxygen.

2. Inadequate Temperature

There are two considerations here. First of all, platies thrive in water whose temperature ranges from 70 to 77 degrees F.[3] They can survive in temperatures that vary somewhat from what they like. But if the water is too cold, they could rush to the top to find relief.

Additionally, water at high temperatures cannot hold as much oxygen as water at cold temperatures. If the water becomes too hot, it could contribute to the oxygen deficiency in the tank. This can happen with tanks that lack heaters. It can also happen with tanks whose heaters malfunction.

3. High Ammonia Levels

As was noted above, poor water conditions will cause distress in your platies, so much so that they will run to the surface to find relief. One symptom of poor water conditions is a high ammonia concentration. The ammonia levels in your tank should be zero.[4] 

This is because ammonia is toxic. It will harm your fish, burn their gills, and affect their ability to breathe, not to mention leaving them susceptible to diseases. Overcrowding can also cause a spike in ammonia concentration. The same goes for overfeeding and a poor cleaning regiment.

4. Disease

If your platies contract a disease that inhibits their ability to breathe, they could rush to the surface to escape what they perceive as an oxygen deficiency. In this case, swimming to the surface won’t help because the water’s oxygen levels are not to blame for their inability to breathe.

Though, that won’t stop them from trying because they don’t know any better. You have to investigate diseases and parasites that affect the gills. Look for signs such as changes in color or ripped fins. Sick platies also appear lethargic and show no interest in food.

5. Food Deficiency

If your platies are hungry, they will frequent the surface. This is because they know that most of their food comes from above. If you haven’t fed them in a while or do not feed them to their satisfaction, they will start swimming at the top in anticipation of their next meal.

Some fish rush to the top whenever they see you because they expect to be fed. But if your platies are always at the top, even before you make your approach, they are probably starving. Once they are fed, they will probably leave the upper sections.

6. Swim Bladder Disorder

Swim bladder disorder occurs when the organ that allows your fish to maintain their balance is compromised due to illness, injury, or even constipation. Fish with swim bladder disorder cannot swim properly, which may cause them to drift to the surface.

When platies are suffering from a swim bladder disorder, it will find it difficult to swim straight. As the issue becomes more severe, the sick fish will turn on its side, floating its way to the top. That typically happens when the platy is overfed. 

7. Personality

It is worth noting that swimming at the top of the tank doesn’t always signify trouble. Like all fish, platies have distinct personalities. They do not always act the same. If one of your platies is spending too much time at the top, it could be merely a personal preference.

There is nothing wrong with a fish choosing to swim at the top even though it isn’t necessarily known for frequenting that section of the tank. You should only conclude that this behavior is a sign of trouble if you notice additional symptoms. Don’t be so quick to rule out that your platies love the top of the tank.

Here are a few articles that are related to this topic and may also interest you:

How to Treat Platies That Swim at the Top?

Because poor water conditions cause this behavior, you can resolve it by improving the tank’s situation, using the following steps:

1. Elevate Oxygen

If your tank doesn’t have enough oxygen, you can solve this problem by purchasing a filter. If you have one, investigate it to ensure that the device is working. A filter will agitate the water. Agitation increases the rate at which oxygen dissolves in the water.

You can also add air pumps and air stones to those locations of the tank that are most deficient where oxygen levels are concerned. For years I leaned on my filter to take care of things until I purchased the Hygger Aquarium Air Stone Kit (link to Amazon). That relatively low-priced device did magic to my tank in terms of oxygenation.

If your tank is overstocked, you can buy a bigger tank or take some of your platies back to the store. The more platies you have, the more oxygen they consume. In case you feel that your tank is too small, I highly suggest checking my reviews for aquarium kits. I mentioned there the precise aquarium that I use and how I was able to save money by getting it.

2. Reduce Ammonia

An overstocked tank can increase ammonia levels. The more platies you have, the more waste they produce. If overstocking isn’t to blame for the high ammonia concentration, perform a 50 percent water change. Do this regularly to keep ammonia levels down.

I would also suggest installing the Seneye Home Aquarium Monitor (link to Marine Depot). That high-end device will alert you when the concentration of ammonia rises. It will also measure the temperature, pH, light exposure, and water level in your tank, alerting you once something had gone wrong (via email or SMS). 

One other solution to this issue is an ammo lock. Once added, it will turn ammonia into ammonium, which is innocuous. Though, the easiest way to keep ammonia levels down is to maintain a clean tank. You have to remove waste, leftovers, and dead organisms.

3. Feed Your Platies Properly

This solution goes without saying. If your platies are swimming at the top because they are hungry, feed them. If your schedule is hectic, add an automatic feeder. That will keep your fish fed regardless of whether or not you are present. I recommend the Eheim Automatic Feeding Unit (link to Amazon). 

However, if you can’t afford an automatic feeder, merely ask a friend or a relative to feed your fish in your absence. Feed your platies the amount they can consume within two minutes. If they finish their meal before that, they probably require a little more.

4. Treat Diseases

The approach you will take to treating your platies will depend on their illness. For instance, flukes need tank level treatment; though, they can’t be cured once they reach advanced stages. If your fish have velvet, you have to raise the water temperature for about a day gradually. Water changes are also necessary.[5]

If slime disease is present, you should check the pH levels. A water change is required, possibly even some aquarium salt.[6] Some diseases require your fish to fast. Others can be resolved with antibiotics. Generally, you should consult veterinarians. They will prescribe the required treatments and drugs.

If your platies are suffering from swim bladder disorder because of constipation, stop feeding them for 24 to 48 hours. If this doesn’t resolve the issue, feed them peas with the skins peeled off. If that doesn’t work, talk to experts. They will recommend some medical solutions.

5. Maintain Ideal Temperatures

If your tank’s temperature is forcing your platies to the top, get a heater. If you already have a heater, make sure it is working. Depending on the size of the tank, you should consider adding more heaters. Here is my review of the device that I use.

Quality heaters will prevent the water from getting too cold for your platies. However, as mentioned, warm water can also enforce your platies to swim upwards. Hence, you should keep the tank away from the windows and reduce the lighting as much as possible.

Why is my Platy Staying at the Bottom of the Tank?

Platies are staying at the bottom of the tank mostly due to underlying disease or poor water conditions. These will result in lethargic platies that tend to sink downwards. However, platies also sit at the bottom once they are dead, asleep, and possibly pregnant.

  • Sleep – Platies are very active fish.[7] And like most fish, they have to sleep to replenish their energy. Don’t be so surprised if your platy sinks to the tank’s bottom whenever the lights are switched off. It is probably sleeping.
  • Dead – A fish that is lying at the bottom might be dead.[8] Dead platies have sunken, cloudy eyes, and they do not respond to stimuli such as bright lights and the presence of food, not to mention poking and prodding. If your platy is dead, you should remove it.
  • Disease – Many diseases create lethargy in platies. They sap the fish of their strength. In some cases, they merely become less active. In other cases, they will sink to the bottom.
  • Lack of Food – A hungry fish will eventually drop to the bottom of your tank. Without food, it can’t sustain its energy levels. This is especially true for very active fish like platies. If you don’t feed them enough, their weakness will eventually drag them down to the bottom. Platies can lose their appetite as a result of stress, bullying, and disease.
  • Water Conditions – Poor water conditions such as high ammonia, nitrate, and nitrite levels, and the wrong pH and temperature can induce distress in platies. They will probably rush to the surface in the beginning. But eventually, once their strength runs out, they will drop to the bottom. This will also happen in oxygen-deficient tanks.
  • Pregnancy – It is relatively commonplace for pregnant platies to frequent the bottom of the tank. If you have both male and female platies in your aquarium, any female platies that spend most of their time at the bottom are probably approaching their delivery date, especially if they show no interest in food.


An essential factor that prompts platies to the bottom sections of the tank is lack of oxygen. Since the upper parts are usually more oxygenated, your platy will choose to swim upwards, gasping for air.

However, that phenomenon could also indicate an underlying disease, such as swim bladder disorders or parasites. In some cases, the water conditions are to blame. Start by examining the ammonia and temperature, and act accordingly.



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