Why Are My Goldfish at the Top of the Tank Water? [Explained]

As a responsible pet owner, one of the most disturbing sights is noticing your goldfish at the top of the aquarium gasping for air.

Under normal conditions, your fish should be at the base foraging for food and only coming out occasionally for feeding. So why is your fish continuously at the surface?

Here is a detailed answer to the question. Read on to find out.

Why Are Gold Fish Continuously Being at the Water Surface?

goldfish on surface

As a normal behavior, goldfish spend most of their time at the bottom of the tank. They are naturally bottom feeders, whether you keep fancy goldfish or other types of goldfish.

However, goldfish may spend more time at the surface than usual. If your fish spend more time at the top, here are a few reasons they do:

Low Dissolved Oxygen Levels

Low dissolved oxygen levels in the aquarium water are one of the main reasons you may find your goldfish at the top of the tank.

The main reason they are at the water surface is that the surface area of water bodies has the highest dissolved oxygen concentration. This is where they can absorb enough oxygen whenever your aquarium water has less dissolved oxygen.

When your goldfish opens its mouth underwater to breathe, water runs over its gills. In this process, the blood in your pet’s capillaries takes in some dissolved oxygen from the water. After picking up the dissolved oxygen, your goldfish absorb oxygen from its bloodstream as its blood circulates.

Hence, when the dissolved oxygen levels in the aquarium water are too low, you will naturally find them at the top of the tank, trying to get enough oxygen.

High Water Temperature

Cold water holds more dissolved oxygen than warm water. Hence, high water temperature means less dissolved oxygen. This is particularly important because a water heater in the aquarium will result in low oxygen levels in the water.

Since warm water holds less oxygen than cold water, many aquarists use live plants, and air pumps to supply oxygen to the water.

However, when the temperature in your tank is high, you can expect to find pets on the surface.

Water Quality

Poor water quality is another reason goldfish stay at the top of the tank. They are trying to access the dissolved oxygen close to the water surface.

Perhaps, the main reason for poor water quality is waste. Goldfish are prolific waste producers, passing it directly into the water. The waste from your pets is usually very high in ammonia.

This leads to health problems because ammonia is toxic to fish. When there is a high ammonia concentration in the aquarium water, fish find it difficult to expel ammonia from their bodies.

Also, the toxins from their excreted ammonia waste dissolve in the aquarium water. This negatively affects their gills and makes it difficult for them to breathe in the water,

This is one of the reasons you may find your goldfish gasping for air at the top of your aquarium.

Why Does Goldfish Blow Bubbles While at the Top of the Fish Tank

goldfish blow bubbles

While at the top and sometimes from the base of the aquarium, your fish may blow bubbles. Usually, this is a sign of bad health, but there are other reasons for this behavior.

Here are some of the most common reasons:


Essentially, goldfish breathe by opening its mouth to gulp some water. After taking some water in, it opens its gills flap to let out the water. This flow of freshwater through its gill chambers allows your fish to access the oxygen in the water.

But in the process of gulping water, your goldfish traps air too. Air pockets are formed when your pet opens its mouth to breathe, and this is part of what produces the bubbles.

Sometimes, you may notice more bubbles appearing like a stream of bubbles from your goldfish’s mouth. This is because your goldfish is breathing quickly as it needs more oxygen. This is usually why they appear to be blowing bubbles while at the top of the fish tank.

Swim Bladder Disease

The swim bladder disease, also known as the swim bladder disorder, could be why your goldfish blows bubbles at the water surface.

Your goldfish’s swim bladder regulates its movement. It is a gas-filled organ that has many functions. But one of its key functions is maintaining buoyancy.

Essentially, it holds air and helps your goldfish float. But your goldfish will find swimming difficult when it holds too much air. It must release some air to regain control. So you may find it producing bubbles in the water when your fish lets go of the excess air.

However, other possible reasons for the swim bladder disorder include injury and infection. You will have to give special attention to these.

Air Pump and Air Stones

Also called air bubblers, an air stone is a great way to diffuse air in aquariums. Air pumps and stones help increase aeration in aquariums. But the problem with these aeration devices is that goldfish and many other freshwater fish find them attractive.

While picking at your air pump and stones, your pet may swallow up some bubbles as it nibbles on them. The extra air could compress your goldfish’s swim bladder and make navigation difficult. However, your fish will eventually release the extra air, which will come out as a string of bubbles from its mouth.

How Can I Increase Oxygen Levels in the Fish Tank?

There are two main ways you can do this for your goldfish. The first is adjusting your filter output to ensure enough surface movement in your tank. The second is by adding air pumps and air stones to ensure that you have additional surface movement in your tank.

Whether it is a hang-on back filter or a canister filter you are using, it must have an output where it sends water back to your tank. You want to position this filter output to ensure that it agitates the surface area of the water in your tank. The movement of the water surface as the output pours into the tank with air ultimately increases the dissolved oxygen level.

An internal power filter works like a canister filter nozzle. If you use an internal power filter, you want to position the filter output to agitate the water surface for adequate water surface movement.

Air stones and air pumps are another excellent way to increase oxygen levels in the tank. It is strongly recommended that every fish tank has at least one.

Many hobbyists erroneously think oxygen levels in the tank increase because the bubbles from the aquarium bubbler dissolve in the water. But that is not the case. It is the bursting of these bubbles at the surface that increases the oxygen.

Another way to increase oxygen levels in fish tanks is to introduce live plants. These plants take in carbon dioxide and release oxygen.

How Can I Ensure Optimal Water Quality?

Water change is the most reliable way to maintain the water quality for your fish. This is because your filter will only convert the high ammonia to nitrite and nitrate, even with the most impressive filter media.

If you do not regularly perform the partial water change, the nitrate levels will increase until it becomes toxic to your fish. The typical response of your fish to the excess nitrate will be to appear at the surface, gasping for air.

Other parameters to check include ph levels, nitrite, and ammonia levels. Also, ensure to remove any uneaten food after feeding.

If you keep too many fish in the same aquarium, it would be best to depopulate the aquarium to reduce waste production.

Bottom Line

This article is a must-read for new tank owners and experienced hobbyists alike because it is crucial to providing a fulfilling life for your goldfish.

It takes a lot to ensure that your fish live a comfortable life. Water quality tops the list, however. You want to regularly test and perform water changes when necessary. If the problem still exists after the regular one-third change, a 50% water change should do the trick.


  • https://oceanconservancy.org/
  • https://www.dkfindout.com/
  • https://www.sciencedirect.com/
Kelly Stanley