Setting up your first aquarium ever and proudly filling it with great-looking fish is pure joy. At the same time, however, realizing something is wrong with your beloved new pets and not knowing what it is can become a real nightmare.

Therefore, knowing to recognize some potential complications before they become life-threatening is vitally important. Respiratory distress is among the most visible signs to follow, so if you are asking yourself “why are my fish breathing heavily and rapidly?”, we are here to help. 

Aquarium Fish Breath Heavily

There may be several reasons hiding behind a rapid and heavy breathing condition. Luckily, most of them can be influenced by you, so you can react promptly and improve your pet’s health state before it gets much worse.

– Lack of Oxygen

Fish that are not able of absorbing enough oxygen from their water can obviously display visible breathing problems. Indeed, their bodies are in such cases literally struggling to function, and they can die pretty soon if their environment is not improved at the soonest.

If you do not have a proper filtration system, use plastic plants only or forget to perform regular water changes, there can certainly be a lack of oxygen across your tank. In such cases, your fish will probably either stick around the top levels gasping for air or will try collecting it from the filter exit.

To avoid such unwanted situations, you should maintain the water pristine clean as well as “keep it fresh”. Regular water changes, good filters and plenty of healthy greenery will all improve the oxygenation levels across the tank.

Furthermore, you may consider setting a simple air stone at the tank bottom, whose main purpose is producing oxygen.

If you are in the middle of an emergency crisis, you can turn to a simple yet effective trick: use a glass or a jar to collect some tank water and then pour it back inside from a fair height.

– Ammonia or Nitrites

In most captivity tanks these should be at zero during all times. Not allowing any ammonia or nitrite to endanger the life of your precious pets is crucial and it can only be kept under control with regular water testing as well as with often partial water changes.

If you are for some reason avoiding cleaning your tank and change its water, even when you have invested in a great filtration system, ammonia and nitrites will rise sooner or later.

Fish produce waste, some meals are left uneaten and some plants can start decomposing, and this can all bring to ammonia or nitrite spikes. If that happens, your fish will be basically “burning out”, unable to breathe.

They can also display visible skin burns or similar irritations, but the only way to be certain is to test your water parameters.

The only successful way of keeping ammonia and nitrites at zero is to regularly clean your tank and the water inside it.

– Aggressive Mates

If you notice a fish panting across a community tank, one of your first guesses should probably be aggressive mates. Indeed, this happens more often than keepers like to think it does, and some fish are easy targets for natural bullies.

When a fish is bullied, it can develop a serious level of stress and, as a consequence, it will be unable of keeping its heart rate normal and will breathe rapidly.

If you are suspecting such a thing is happening across your tank, the simplest way to confirm that is by carefully observing your pets. How do they interact, and is there any fish which keeps swimming away from the rest of the group?

If you notice any behavioral changes such as fin nipping or even some visible signs like injuries, you should probably intervene and isolate your bullied fish for a bit.

In order to avoid such stress in the future, make sure to choose your tank mates wisely and according to their natural instincts. And remember, you should always keep an eye at their behavior.

– Birth Giving

If you own a pregnant livebearer fish, please keep in mind that your fish will have more trouble in giving birth than its egg-layer tank mate will have to scatter the eggs.

Indeed, livebearers have to keep their fry inside them for a few cycles and wait for them to become fairly large before giving them birth. This, obviously, requires much more effort from their side and they can start panting during the process.

Birth giving is a completely normal and natural happening and there is nothing special you can do for your pet here, other than ensuring she has all the best living conditions.

– Temperature Shock

It is unavoidable for a fish to feature breathing difficulties if it has been subject to a temperature shock. Indeed, the same happens to people when exposed to such abnormal spikes.

The easiest way to verify that is by checking your thermometer. If the temperature is much different than it was earlier, you may be sure this is what is causing your fish to struggle.

This happens mostly when the heater is malfunctioning or when a new fish is introduced to the tank without a prior period of adjustment.

You should be aware of the ideal temperature ranges for your fish species and you should always maintain such levels stable.

– Stress

Any stress trigger can lead to a compromised immune system and develop breathing difficulties among your fish. Therefore, please avoid these as much as possible. New tanks, inappropriate environment, travel, aggressive tank mates, or various diseases can develop stress.

– Disease

Fish breathing with trouble when being sick should not come as a surprise to anyone. This can be caused because of purely respiratory diseases, but also because of others that simply do not allow your fish of functioning normally.

Wrapping Up

Every fish can sooner or later start breathing rapidly or heavily. Sometimes, however, such conditions can be either avoided or improved by proper human care.

Learning to distinguish the various scenarios and knowing how to react is, therefore, vitally important.

Written by Fabian

Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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