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Fish at The Top of The Tank Blowing Bubbles: 4 Easy Solutions

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Quite frequently, I notice worrying issues in my tank. For example, there were times when I saw my fish swim at the top of the tank and consistently blow bubbles. The more I investigated the issue, the more different reasons and solutions I found. Now, I am willing to share all that I’ve learned.

Fish typically blow bubbles at the top of the tank due to oxygen deficiencies. To exploit oxygen residues, they breathe more rapidly, producing bubbles in the process. Nevertheless, fish also blow bubbles when the water quality deteriorates, causing ammonia and nitrates to elevate.

As we move forward, I will share a few useful techniques to treat fish that blow too many bubbles. Following those steps will ease the distress your fish are probably experiencing. I will also teach you how to get rid of bubbles in your aquarium to make it look more clean and appealing.

Why do Fish Blow Bubbles at the Top of the Tank?

Bubbles are nothing new to aquariums. They are generated by filters, aeration devices such as air stones and pumps, and live plants. You can also produce bubbles in an aquarium by agitating the water. 

Ultimately, unless you hate their impact on your aquarium’s appearance, they are not necessarily a significant concern. Nevertheless, the same cannot be said for bubbles produced by fish, mostly if those fish have chosen to frequent the tank’s upper sections. 

Some notable causes of such behavior in fish include:

1. Frequent Mouth Movements

Fish use their gills for breathing. The organs absorb oxygen from the water, dissolving it into the blood. The creatures can draw water into their mouth, allowing it to wash over their gills to aid in the breathing process. On occasion, when a fish opens its mouth, air will escape. 

If that air creates a pocket, it will form a bubble that will linger for a moment before popping. If air keeps escaping whenever the fish opens its mouth, the creature will appear to blow bubbles.[1] You may see this in fish that are eating the food you sprinkled on the surface of the water.

2. Lack of Oxygen

The blowing of bubbles in fish isn’t always innocent. In many cases, fish that blow bubbles at the top of the tank are actually gasping for air. In other words, the oxygen levels in the lower sections of the tank are so low that the fish is struggling to breathe, which is why it is lingering at the surface where oxygen levels are so much higher.

And because it keeps opening and closing its mouth, the rapid mouth movement (and any air that might escape) will eventually produce bubbles. If a fish is struggling to breathe, it will become more active, swimming rapidly before eventually growing lethargic, particularly in situations where the hypoxia persists.[2]

I even dedicated an entire article to fish that rapidly move their mouths. If that is your case, I highly recommend checking that out. I also included four quick solutions that will take care of your fish if it suffers from oxygen deficiency.

The notion of fish running to the surface to get oxygen might sound ridiculous to some of you because, as was mentioned before, the creatures use their gills to extract oxygen from the water. They are not built to draw oxygen from the air.

However, a fish gasping at the top of the tank isn’t necessarily breathing air, not unless it is a betta fish with a labyrinth organ that allows the creature to breathe air. Most fish are intelligent enough to stay below the surface of the water, only extending their mouths far enough to consume the thin layer of oxygen-rich water that is directly touching the air.

3. Bubble Nests

Species such as bettas and gouramis have a mating ritual that involves the blowing of bubbles.[3] These fish gulp air from the surface, using it to blow bubbles, which eventually congregate at the top. You typically see such behavior in male fish. 

Once they accomplish this task, they will seek out and guide a female companion to the bubble nest. These fish also encase their eggs in bubbles. Aquarists that own bettas and gouramis are accustomed to seeing bubbles in their tanks because these fish are always blowing them.

4. Gas Bubble Disease

Some fish eat bubbles from time to time. They practically nibble on them. If they swallow air because of that, they might eventually push it out through the mouth or gills as bubbles. Those fish naturally do that at the top because bubbles rise to the surface.

In the worst-case scenario (where the air isn’t expelled as bubbles), the fish in question may develop gas bubble disease. That is where supersaturated gasses are absorbed into the fish, clustering under tissue and causing swimming problems, possibly even death.[4]

5. Low Water Quality

The quality of your water will affect the health of your fish. If you fail to maintain the tank, toxins like ammonia will spike. That is a problem because ammonia can harm the gills. Because fish use their gills for breathing, any damage they suffer will lead to suffocation. 

Fish that are living in tanks whose concentration of ammonia is too high will gasp for air. In some cases, they will rush to the surface in search of relief. Though, because their suffocation results from damaged gills rather than an oxygen deficiency, the oxygen-rich water at the top won’t offer the relief the fish desire.

You typically see this phenomenon in small tanks that are poorly maintained. You can also expect a similar reaction among fish that have developed illnesses such as the Flukes that compromise the gills’ functionality.[5]

I’ve previously mentioned that issue in a different article, where I discussed what makes goldfish frequently open and close their mouths. Even if you don’t own goldfish, that article can benefit you since it includes seven tips that will help fish in distress.

6. High Temperature

Is your tank too hot? That is a valid question because the warmer the temperature, the less oxygen it can hold. If you have permitted your aquarium’s temperature to spike, your fish will rush to the surface to escape the low oxygen levels below. 

They will also gasp for air, producing bubbles as a result. That is very likely to happen in tanks that are adjacent to a window. Temperatures also spike in relatively small tanks and bowls in particular.

How to Treat Fish That Blow Bubbles at the Top?

If you have Aphrophilus species in your aquarium, such as bettas and gouramis, that build bubble nests, they don’t require treatment.[6] They are supposed to blow bubbles. Yet, if your fish do not fall within that category and yet they are still blowing bubbles, you should respond to their behavior with the following steps:

1. Conducting Water Changes

A lot of problems in an aquarium can be solved with a water change. A water change will lower the temperature, remove toxins like ammonia, and eliminate any pollutants and parasites in the tank responsible for diseases.

If you are new to aquariums, you should create a schedule that includes regular water changes. If you have some experience with aquariums and change the water regularly, you can still perform a water change ahead of schedule if your fish show clear signs of distress.

Your maintenance regiment should also involve vacuuming the substrate and removing dead organisms that might raise the concentration of ammonia. On that matter, I highly recommend checking the API Aquarium Test Kit (link to Amazon).

That bundle will measure your pH, ammonia, nitrites, and nitrates. Within five minutes, you’ll be able to tell if the toxins in your aquarium are too high. In case they are, I would recommend performing more frequent water changes while cleaning the substrate properly.

Bear in mind that even after a water change, ammonia can remain high. I even dedicated an entire article to that issue. If you suffer from persistently elevated ammonia levels, I highly recommend checking what I wrote.

2. Improving Aeration

Once you change the water, you should also improve your tank’s aeration, particularly if your fish was blowing bubbles at the top because of an oxygen deficiency. The water change will provide relief, although you are still encouraged to identify the factors that caused the oxygen deficiency. 

If the water was too stagnant, get a more powerful filter that can provide proper agitation. Consider adding air stones and pumps that will ensure that oxygen is evenly distributed throughout the aquarium.[7] I personally use the Hygger Aquarium Air Stone (link to Amazon).

3.Treating Gas Bubble Disease

The supersaturated gasses that cause gas bubble disease have been attributed to a decrease in pressure and an increase in temperature and salinity. You can alleviate the disease’s symptoms by moving the afflicted fish to an aquatic environment with higher pressures.[8] 

That is typically done by introducing the sick fish to relatively tall tanks. That will allow the fish to exploit the hydrostatic pressure and get rid of the trapped gas. It is also vital to improve aeration in the tank.[9]

4. Adjusting the Temperature

Maintaining the right temperature in an aquarium isn’t that difficult, not when you have a functional heater. Some heaters malfunction without the knowledge of the aquarist. That causes them to overheat the water.

If your tank’s temperature is too high, you should start by inspecting the heater to ensure that it is working correctly. If your current device doesn’t work correctly, I highly suggest considering the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon). I also reviewed it here.

That excellent heater will keep your water temperature stable, ensuring that unnecessary spikes do not occur. As you can see in my review, the fluctuations with that heater are minimal, which is essential to your fish’s general state.

You should also keep the tank away from air conditioners and the direct sunlight coming through an open window. If the ambient temperature keeps raising the tank’s temperature, you can reduce it by using a fan to blow across the surface of the water. It would help if you also considered removing the aquarium lights.

How do I Get Rid of Bubbles on Top of My Fish Tank?

Getting rid of bubbles on top of fish tanks involves these steps:

  1. Remove debris and leftovers to prevent protein coating.
  2. Avoid using soap while cleaning the tank.
  3. Place the filter outlet below the waterline.
  4. Introduce floating decorations and gentle currents to prevent bubble nests formation.

You don’t have to tolerate the bubbles on top of your fish tank, especially if you hate their impact on your aquarium’s appearance. There are ways to either remove or prevent bubbles from forming, including:

1. Aquarium Maintenance

People expect the bubbles that form in a tank to pop. However, that won’t happen if the protein has coated the bubbles in the water.[10] The presence of protein in such quantities is a sign that your tank is dirty. 

The solution is to do some cleaning. Start by removing all the pollutants and debris from the water. Clean the substrate, filters, and decorations. I would also recommend performing more frequent water changes.

2. Washing Soap Leftovers

If your aquarium is tainted with soap, it will develop bubbles with a colored tint.[11] Soap is also dangerous for fish. It has components that will poison your fish, possibly killing them in the long haul. 

Once you notice bubbles with a colored tint in the water, move the fish to a separate tank before draining the tainted aquarium. Rinse it thoroughly, not just the walls and bottom of the aquarium but the substrate and decorations.

3. Positioning the Filter Properly

The filter outlet can generate bubbles by agitating the water. Those bubbles will eventually rise to the surface. That is common in filters whose outlets are situated above the water. Their position causes the water they release to trap air. 

You can solve this problem quite quickly by positioning the outlet beneath the water surface.[12] If you find it hard to lower the filter, you may raise the water level. Even when the outlet is positioned underneath the surface, oxygenation will continue.

4. Bubble Nests

Bubble nests promote mating among bettas and gouramis. Rather than eliminating these nests, you should instead endeavor to encourage their construction by maintaining a gentle current, adding floating decorations, keeping the water clean, and providing foliage.[13]

You can reduce the possibility of bubble nests forming by populating your tank with female bettas and gouramis. That is because primarily male fish construct bubble nests. Though, on occasion, female fish will build them as well. As such, this tactic isn’t guaranteed to work.[14]


If your fish is blowing bubbles at the top of the tank, it is probably suffering from an underlying issue. To overcome the distress, fish breathe more rapidly, producing bubbles as a consequence. Therefore, it would help if you checked for stress factors.

Start by checking the water quality (using a testing kit) and the temperature. If everything is within the ideal range, I suggest introducing a few airstones to the aquariums. Those will create bubbles. However, you will also improve your tank’s oxygenation.