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Why Do Fish Open and Close Their Mouths All the Time?

Many people are fascinated by aquatic life. Observing a fish tank is a peaceful and enjoyable pastime for aquarium hobbyists. After all, watching fish actively swim about in all their colorful glory is usually the reason why people get involved in the hobby to begin with! But is it normal for them to open and close their mouths all the time and should you be concerned with this behavior as a pet owner?

In most cases, when fish linger near the surface while opening and closing their mouths frequently, it’s usually a sign of oxygen depletion in their aquatic environment. The more water they take in with their mouths, the more air they can get over their gills and into their bodies. If your fish appear to be ‘panting’ or struggling to breathe, you should test the oxygen levels in your aquarium immediately.

Now that you know a lack of oxygen will cause your fish to open and close their mouths frequently, let’s explore this topic in more detail. As we move forward in this article, I’ll discuss what typical ‘breathing’ behavior looks like for fish and how to determine if their panting behavior is the result of low oxygen levels in the water. I’ll also explain how to use an oxygen meter to test for dissolved oxygen amounts.

So, if you’re ready to learn all you need to know about fish and their ‘breathing’ habits, then let’s get started!

What Does it Mean When Fish Keep Opening and Closing Their Mouths?

Opening and closing their mouths frequently is not common for most fish. This behavior is usually a sign of low oxygen levels in the water. Because fish breathe through their gills, opening and closing their mouths allows more water (and thus more oxygen) to pass over their scales and through their bodies. If the oxygen concentrations in the water are low, they’ll need to do this more often.

How Many Times Does a Fish Open and Close Its Mouth in 1 Minute?

On average, a fish will open and close its mouth up to 50 times in 60 seconds! Since colder water can hold more dissolved oxygen than warm water, cold-water fish that thrive in temperatures below 68 degrees Fahrenheit (20 degrees Celsius), tend not to open and close their mouths as often as tropical fish that live in water ranging from 75 to 80 degrees Fahrenheit (24 to 27 degrees Celsius).

Why are My Fish Panting?

Rapid breathing or ‘panting’ is common when new fish are introduced to a community tank. The shock of being transported and then placed in an unfamiliar environment will elevate stress levels in fish, causing them to pant. Harassment from other fish will also cause this behavior, so keep an eye on your aquarium if you notice it happening often.

Why are My Fish Breathing at the Surface?

Fish will often linger near the top of the tank to ‘breathe’ easier, since dissolved oxygen (where water and air combine) is higher along the surface. This behavior isn’t normally cause for concern, unless it appears as though your fish are struggling to respire. Poor water quality could also be the culprit so be sure to test the pH level of the water regularly as too much ammonia can be deadly for fish.

Why is My Goldfish Opening Its Mouth?

Goldfish, for example, will open and close their mouths frequently when oxygen levels in the water are too low. This hyperventilating action increases the flow of water over their bodies and allows more dissolved oxygen into their gills. This behavior is typical of overstocked tanks or in aquariums where water temperatures are warmer with little to no circulation.

How Do Fish Gills Extract Oxygen from Water?

Fish gills function like lungs and are branching organs near the sides of fish heads. They contain tiny blood vessels or capillaries that absorb oxygen while excreting both carbon dioxide and ammonia. As a fish opens and closes its mouth, water rushes over its gills allowing blood in the capillaries to pick up the dissolved oxygen in the water and distribute it into the body. This action is vital for fish survival.

How Do I Know if My Fish Tank has Enough Oxygen?

If your fish linger near the surface and appear to be gasping for air, there’s probably not enough oxygen in the water. As well, should you notice your fish hovering near the filter output, that’s usually another tell-tale sign of low oxygen levels. Fish that swim about freely in the middle of the tank and don’t open and close their mouths too often are likely getting enough oxygen.

How Do I Give My Fish More Oxygen?

Aerating the water is the best way to give your aquarium fish more oxygen. This is done by installing a good filtration system as well as an air pump. Filters increase water movement, thus helping to circulate dissolved oxygen throughout the entire tank – near the surface (where oxygen exchange takes place) as well as along the bottom.

Air pumps add oxygen-filled bubbles to aquarium water. They are highly effective (yet affordable) and work to maintain adequate oxygen concentrations in a variety of tank sizes. A great one to check out online through Amazon is the Tetra Whisper Air Pump. Not only does it increase air flow, but it also adds visual interest when the bubbles catch the light and illuminate fish movement!

Are Air Bubbles Good for Fish?

Air bubbles created by an aquarium pump or air stone are very beneficial for aquarium fish. These bubbles create movement and help oxygenate the water when they ‘pop’ near the surface. A well-aerated aquatic environment improves the health of not only the fish, but also the plants and other creature in the tank.

How Can I Oxygenate My Fish Tank Water Without a Pump?

If you have a small aquarium or simply don’t have the budget to invest in an air pump at this time, you can oxygenate the water using a cup or a pitcher. Simply dip the cup or pitcher into the tank, fill it with aquarium water, remove it from the tank, and then pour it back in! Doing this a few times will allow the water in the cup or pitcher to pick up oxygen from the air, which can then be distributed it into the tank.

Can You Over Oxygenate a Fish Tank?

Over oxygenating an aquarium is possible and can be dangerous for fish. Too much oxygen in the water can result in gas bubble disease whereby fish expel high amounts of carbon dioxide, causing their skin to bubble and their eyes to bulge out! Another source for this disease could be a rapid increase in nitrogen concentrations in the tank. At this point, you should be testing the water for toxic ammonia levels asap!

Conclusion

To conclude, when fish open and close their mouths often, it’s usually due to a lack of oxygen in their aquatic environment. This ‘panting’ action allows fish to get more water over their gills and thus more air into their bodies. Should you happen to notice this behavior occurring more frequently than usual with your fish, then it’s time to test the oxygen as well as ammonia levels in your aquarium.

I hope this article answered your questions regarding why fish sometimes appear to be hyperventilating. Thanks for reading and good luck with your aquarium hobby.

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