Why Are My Tropical Fish Gasping For Air? – The Three Most Likely Reasons

If you are asking yourself “Why are my tropical fish gasping for air?” You’ve come to the right place! The main reason why tropical fish are gasping for air is because they are in an environment with too much carbon dioxide (CO2). This can be caused by several different things, such as:

1. The Amount Of Time Since The Last Water Change

Freshwater aquariums need to be changed around 25% every 2 weeks, and salt water aquariums should be changed around 20% per month. Regular water changes help keep the levels of CO2 down within the tank.

2. Inadequate Filtration

Fish create waste which make the water dirty, so there needs to be an adequate filter that is taking out this waste often enough. If the filter isn’t strong enough to process all of the waste, it leads to high levels of carbon dioxide in the water.

3. Inadequate Tank Size

The more fish, the more space they need. This is because all fish produce CO2 as a waste product of their metabolism, and the bigger the volume of water in a tank, the less concentration of CO2 there is. So even if a filter is taking out waste constantly, it will still build up over time if the tank isn’t big enough to accommodate it.

If any one or all of these things are true for your aquarium, then you may have problems with your tropical fish gasping for air.

If you have a freshwater aquarium, then you will want to change your water 25% every 2 weeks.

For saltwater tanks, it is recommended that you change 20% of your water per month.

You may also need to upgrade or change your filter so that more waste is being kept out of the tank in the first place.

If you are already doing these things and still have problems with tropical fish gasping for air, then consider getting a bigger tank because this will provide enough space for oxygen to be replenished in between cleanings/water changes.

A good rule of thumb is that for each inch of fish there should be 1 gallon of water – so for example if you have 5 fish all around 2 inches in size you would need to have at least a 10 gallon tank.

2 silver fish in a tank with aquatic plants

Do Fish Need Oxygen In A Tank?

The short answer to this question is yes. All fish require oxygen for their survival. Even though they can survive in water that does not have a lot of oxygen in it, they will be much more likely to develop health problems when kept in an environment with less than ideal levels of oxygen.

How Do Fish Get Oxygen In A Tank?

Fish acquire oxygen from the water through their gills. Think about a fish as being a big sponge that soaks up water and whatever else is inside of it – including carbon dioxide (CO2) which forms from the fish’s metabolic processes and also from decaying organic matter such as uneaten food or dead plant/animal life. However, since CO2 is denser than air, it remains near the bottom of an aquarium where it can quickly become a problem for fish that live there. This is why filtration systems are so important – they keep this harmful CO2 out of the tank by forcing water through filter media which traps all organic materials that could potentially decay.

Why is carbon dioxide dangerous?

Carbon dioxide (CO2) in the air causes us humans to have difficulty breathing because it reduces the percentage of oxygen in our environment by creating a ‘vacuum’ effect which sucks the oxygen out of the air around us. In an aquarium, this vacuum effect causes oxygen levels to drop by taking up space in tanks and displacing less dense oxygen molecules with its own higher concentration. When carbon dioxide starts to accumulate, the potential for hypoxia sets in which is when an organism has so little oxygen breathing becomes difficult if not impossible.

How Do You Know If Your Fish Is Struggling To Breathe?

  • Look at the gills. These are the feathery things on the sides of your fish behind its head. If they are moving rapidly in and out, then it is likely that your aquarium has too much CO2 in it.
  • Watch if your fish come up to breathe at the water’s surface. If they repeatedly do this, then there is probably not enough oxygen in the tank for them.
  • Watch the coloration of your fish – if they are very bright or dark colored, with bright red/orange colors (especially with saltwater fish) then their blood vessels may be more visible than usual due to them trying to get more oxygen into their bloodstreams when there is not enough available in the tank.
  • Look at the size of your fish – if they are much larger than other ones in your aquarium, then they may be gasping for air because there is a lack of oxygen and not too much CO2 present. This is because larger fish need a bigger tank! So make sure you have received accurate recommendations from a pet store as to what size tanks tropical fish need based on their sizes.

These are all signs that your tropical fish might be struggling to breathe, so make sure you check up on them to ensure they are healthy and thriving in their respective homes. If not, then consider what changes you can make so that the environment they live in more closely resembles their natural habitats.

How Do I Know If My Fish Tank Has Enough Oxygen?

If your fish exhibit any of the signs mentioned above, you may have a problem with the amount of oxygen in your tank. You can test the amount of dissolved oxygen in the tank by using an instrument called a Dissolved Oxygen Meter. A Dissolved Oxygen Meter works by placing a probe into the tank (don’t worry, it doesn’t hurt the fish) which collects data on the amount of oxygen present in the water.

There is also another type of instrument you can use for this purpose called an Oxygen Kit. An Oxygen kit works by having you put certain chemicals into your aquarium, and then waiting an hour or two before dipping out a sample of water to be tested with another instrument. You can buy either of these instruments at your local pet store or online.

How Do I Increase Oxygen In My Fish Tank?

One of the most important things to do in order to increase oxygen is to make sure your tank is clean and has a strong filter – if there isn’t much dirt or waste in there, then most of the decaying material will never even become an issue with carbon dioxide because it won’t be breaking down at all.

Another thing you can do is add airstones which will create oxygen bubbles in the water, which will help increase oxygen saturation. You can also try adding an air pump to the tank.

Aquatic plants will also help with this, as they release oxygen into the water during photosynthesis. If you have a lot of plants in your tank then it is likely that the level of oxygen saturation will never become an issue because there is so much being produced from all those leaves.

Is Too Much Aeration Bad For Fish?

No, not really. It’s actually good for tropical fish tanks to have a bit of aeration in them – it helps stop stagnation which can lead to problems like pH shock and ammonia spikes. If your tank is constantly receiving bubbles then you do not need to worry about this at all.

What If My Fish Is Gasping For Air After Water Change?

One of the most common reasons why fish gasp for air after a water change is because they are in shock. This happens when you move them to different water, or if you significantly changed the temperature (more than 5 degrees) in your tank. When doing a water change try to ensure that you keep the tank at a consistent temperature and pH to minimize this from happening.


How do you increase oxygen in water naturally?

There are many ways to increase oxygen in water naturally – one of the best options is to put an airstone into your aquarium, but if that isn’t possible then you can also try adding aquatic plants like hornwort since they release lots of oxygen during photosynthesis [source].

Is there a difference between dissolved oxygen and atmospheric oxygen?

Yes there is! Dissolved oxygen occurs within liquids (including water), whereas atmospheric oxygen takes place above water. This means that when you do an aeration process, the bubbles that come out contain atmospheric rather than dissolved oxygen.

pearl gourami

How can I add oxygen to my fish tank without a pump?

One of the best ways to oxygenate your tank without using an aerator is to use aquatic plants like hornwort, or even some types of algae. As these organisms photosynthesize oxygen will be released into the water, making it easier for fish to breathe.

What are oxygen tablets for fish?

Oxygen tablets for fish are small white pieces of chemicals that you place at the bottom of your tank. They work by breaking down and releasing atmospheric oxygen into the water, making it much easier for tropical fish to breathe.

Oxygen tablets should only really be used in the short term or if you are transporting your fish.

Why Are My Tropical Fish Gasping For Air? - Conclusion

If your fish are gasping for breath it’s likely due to too mych CO2 in the tank and not enough oxygen. Inadequate water changes, filtration or tank size are likely to be the cause. You will need to take urgent action otherwise the health of your fish will suffer!