Why Are My Fish Staying at the Top of the Tank? – 11 Reasons

why are my fish staying at the top of the tank

If you are finding the fullest answers for your question of “why are my fish staying at the top of the tank”, don’t overlook my suggestions here.

Through this article, you will definitely detect the main reasons that lead to your problems, from the normal (like sleeping or eating habits) to the more troublesome ones (such as diseases). Are you ready for new fish keeping tips now? Just scroll down for more.

List of Possible Reasons

Normal Reasons

1. Asking For Food


While there are some types of fish that love eating sinked food, some others prefer floating “feast”. Therefore, it’s not weird to see your beloved fishes swim at the top of the tank just to beg for their food.

2. Responding To A Change In Their Living Area

Fish are all likely to immediately react to even the smallest changes in their living environment and that might be the reason why your fish floating at top of tank.

This situation also happens with new fish since there might be some differences between your tank and their previous living place. Just ensure that your pets come back to normal in a few minutes later because it shows that they will be fine.

On some occasions, fish keep swimming to the top because of bullying from the other tankmate. Based on that, you should avoid leaving peaceful fish (like honey gourami, diamond tetras, etc.) with possible bullies (like guppy fish).

3. Enjoying Exploring Their Surroundings


It’s normal to see your fish staying at top of new tank or swimming around when you first introduce them to their new home. That’s all because they want to know more about their living areas.

Instead, if you see them hiding or staying at the same place over time, they might feel a bit uncomfortable there.

4. Taking A Nap

Just like the eating habits, each kind of fish has distinguished favorite places to sleep and some will enjoy taking a nap near the surface of your tank.

Concerning Reasons

1. Overly-High Or Low Temperature


Whenever your tank water becomes too hot or too cold, your fish will tend to stay in a more comfortable area. However, the uncontrollable water fluctuation badly affects your pets’ health and can even lead to death.

Then, if it’s the case, you should fix the issue as soon as possible and employ a more accurate thermometer.

Note: Distinct types of fish will require different water temperatures in order to thrive or survive. For instance, betta fish need their tank to be around 78 to 80 degrees F while goldfish only require a temperature around 68 to 74 degrees F.

2. Oxygen Insufficient


Your fish hanging out at the top of the tank for too long might be a sight of lacking oxygen. Maintaining the oxygen level inside your tank is vital to protect your pet’s health. Once mentioning about oxygen inside a fish tank, you should think of these smaller reasons first, such as:

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  • Problems with the aerating system may cause an oxygen shortage, so that thinking of having a new one or seeking for oxygen-supplying sources (such as live plants).
  • Warmer-than-needed tank water, which is higher than around 75-80 degrees F, can hold less oxygen than normal. As a result, your fish stays at top of tank to get more air.
  • Overcrowded tanks can make the oxygen level get lower quicker than expected and the organic waste will also build up faster.
  • Lack of lighting can cause plants in the aquarium to reverse photosynthesis, and instead of taking oxygen to convert to CO2, they will absorb O2 to convert to CO2.
  • Lack of water flowing minimizes waves that aid in the even distribution of oxygen throughout your tank. As a result, this might lead to an oxygen deficit.
  • Applying wrong kinds of medicines/chemicals might also decrease the O2 level in your tank water.


3. Ammonia Accumulating


There are quite a lot of reasons leading to the rise of ammonia, such as fish waste, wrong water use, or the bacteria accumulation. Once meeting this issue, you will see your fish try to gasp for air, have bloody patches and lose their appetite.

If you only see your fish quit eating but not gasping, chances are the underlying causes lie in the water temperature or some illnesses, like flukes or else. So, be careful and detect the right cause in order to fix it properly.

Moreover, ammonia overloading can also kill your fish or be extremely harmful to their brains, body and organs.

Diseases Reasons

1. Swim Bladder Disease


When you see that your fish are struggling to swim properly, float upside down or move sideways, they are having this swim bladder disease/disorder. Although the disease won’t 100% kill your fish, it’s pretty dangerous if you neglect all the symptoms.

Genetic, constipation, infections are the possible causes of this common disease; yet, you should also think of some other external reasons, such as water parameters fluctuation or poor tank water quality. To know exactly, please bring your pet to the nearest vet.

2. Ich


No matter if you are having a marine or a freshwater aquarium, your fish are all susceptible to Ich. It’s because Mycobacterium erinaceus (the bacterium that causes Ich) can live in any water conditions.

Remember that if you leave your infected pets alone, they will die within 4 to 7 days. Otherwise, this disease might quickly spread to the tank’s other inhabitants.

As a result, if you notice any early indicators of the problem (such as small white spots floating on the surface, color changing on fish’s gills, or your pet suffering respiratory difficulties), you should consult a professional veterinarian right away.

3. Aeromonas Hydrophila

Aeromonas Hydrophila is the next fatal disease on this list and it mostly happens with freshwater fish (like catfish or bass). This sickness makes your fish swim weaker, paler gills, and eat less.

The main causes of this disease are the stress from lack of nutritions, overcrowding and poor tank water quality.

4. Flukes

Losing weight, cloudy eyes, and gasping for air continuously are all common symptoms of these deadly flukes. These bacteria stay on fish’s gills, skin, or fins and can be spread to your tank through plants or new members.

What Do I Need to Do if My Fish Staying at the Top of the Tank?


As listed above, you can see that there are various issues leading to these troublesome problems, and here are what you should do:

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  • Monitor the symptoms closely to know whether it’s a normal reason or a concerning one.
  • Bring your fish to the vet immediately if they really show the early signs of those listed illnesses above.
  • Do the water test to check the ammonia, pH levels, and the other water parameters to detect the concerning reasons in more detailedly.
  • Check the filter to see if it works nicely or not.
  • Think of installing a new thermometer to assure providing enough oxygen to your fish as well as maintaining a stable water temperature for your pets.


How to Prevent This Problem?


With different causes, you will need to perform distinguished actions to prevent. However, there are some general things you can refer to and apply into your situation:

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  • Keep your tank clean as contaminated water can cause various deadly diseases.
  • Do water changing more often to avoid fish waste/toxins building up after time. Remember to do partial alteration only to avoid the water shocking after water change.
  • Employ a fine thermometer in your tank to manage the water temperature better.
  • Never skip cleaning filters to decrease the waste stuck in them and affect the efficiency of the machine.
  • Test the water parameters frequently to keep the pH, ammonia, etc. staying at the safe range.
  • Always separate newly-bought fish from the old ones for a time before letting them live together in order to prevent external diseases from spreading among tank members.


Frequently Asked Questions


What does it mean when fish stay at the top of the tank?

It means many things. For example, if your fish staying in top corner of tank, it might mean your pet’s cold. On other occasions, your beloved fishes swim at the top of the tank because they are stressed or finding more oxygen.

Why does my fish stay at the top of the tank after a water change?

It’s all related to significant changes in the tank water’s parameters/chemistry (particularly the oxygen level), which may overwhelm and stress your pets out. As a result, the fish will tend to stay near the surface of the tank in an attempt to get more oxygen and cope with the changes.


Do the answers above satisfy your question of “why are my fish staying at the top of the tank?”? I hope that my provided information today is all helpful to you and can assist you in the future.

Otherwise, if you have any other questions, feel free to comment down below and let me know. Your contribution will motivate me a lot. Thanks in advance!