Even though fish do not have lungs, they do get oxygen through their gills. However, bettas, and other labyrinth fish, are unique in that they have a labyrinth organ in addition to their gills. While they do rely a great deal on their gills, they have another way to get oxygen.
Betta fish do need oxygen, but unlike other fish, they need to be able to extract oxygen from both the water and from the air. Most fish do not need access to the air, so a very low lid, or even one touching the water, does not make a difference. In addition, other fish need highly oxygenated water in order to survive, but the betta does not.
In this article, we will discuss the labyrinth organ, bubblers, surface agitation and gas exchange, film on the surface of the water, and gills.
Think of the labyrinth organ as a primitive pair of lungs. The betta cannot solely rely on this organ, but it is necessary for the betta to be able to use this organ whenever they need to. They tend not to rely wholly on either organ, so they must be able to access both the atmosphere and the water.
In the wild, bettas come from very warm areas, and the areas they come from are also normally stagnant. The water is neither nasty nor polluted and expands for several miles.
The higher the temperature, the less dissolved oxygen there will be in the water. The less surface agitation, the less dissolved oxygen. Therefore, the natural habitat of the betta has low dissolved oxygen, so they needed to be able to find another source to breathe.
Having a bubbler is not a bad idea in an aquarium, as it increases gas exchange at the surface. Extra aeration is always a plus, especially in a tropical aquarium, since the warmer water does not hold much dissolved oxygen on its own.
If your betta fish is the only inhabitant of the aquarium, you do not need to add a bubbler unless you have a film on the surface. The film will look reflective and can interfere with the functioning of a betta’s labyrinth organ but can be removed by extra surface agitation.
On the other hand, if you do have other inhabitants in the tank, you should add a bubbler to increase the oxygen levels. The only exception to this rule is the mystery snail, a subspecies of apple snail. These snails also come from warm and relatively stagnant water, and as such, they have developed a breathing siphon that allows them to take oxygen from the atmosphere. Just like the betta, they do need to be able to use the siphon and access the air or they will die.
Bubblers can also help with temperature problems caused by a lack of flow. Betta filters often have very low flow because a betta’s long fins make it difficult for them to swim properly. Therefore, strong filters will prevent them from swimming, so they are kept with filters with very low flow.
This sometimes cause issues with their heaters. If the flow is not adequate, the heater will only be able to heat the water directly around it, and most of the tank will be too cold for the betta. If this is the case, you must remedy the situation as soon as possible.
Surface Agitation and Gas Exchange
The reason that bubblers and surface agitation increase gas exchange is because it increases the surface area of the water. Gas exchange is the exchange of atmospheric gasses with ones in the water. Oxygen is depleted in the water and is only replaced through gas exchange with the surface; carbon dioxide leaves the water and oxygen enters it.
When the bubbles expand and ripple the surface of the water, they slightly increase the surface area, and the agitation they produce is great for increasing gas exchange. This is also a method used to remove chlorine from water, though this should be done in the absence of fish.
In addition to a bubbler increasing gas exchange, they also pump in air from the outside. As the bubbles travel up to the top of the tank, some of the gasses dissolve into the water before they make it out. Therefore, a bubbler increases the oxygen content of an aquarium in more than one way.
If you do not have an air pump and therefore cannot use a bubbler, a hang on back filter may be a better solution. These filters have a “waterfall” part, which creates quite a lot of surface agitation and bubbles at the area where they cascade down into the aquarium.
Film on Surface of Water
As previously mentioned, a film on the surface of the water is often a protein film. This film is normally caused by excess decaying matter, more often than not it is fish food. While it is possible to make or buy a protein skimmer (which will do an excellent job of cleaning off that film) it is often not at all necessary.
The film is an issue for labyrinth fish and normal fish alike, as it interferes with the labyrinth organ and reduces the gas exchange at the surface of the water, so all kinds of fish will have trouble breathing. Other things can also cause a film on the surface, including lotion, which does not belong in an aquarium.
If the film does not go away with increased agitation, you should consider other possible causes. Increase your vacuuming of the substrate and reduce feeding for a few days. Contact your water treatment company and ask if they have recently flushed or cleaned the lines. Sometimes the chemicals used will cause a film, but this often kills off all fish that come in contact with it.
If you believe the film could be lotion or soap, do two very large water changes of at least 80%. This will greatly reduce the amount of contaminant in the aquarium, though more water changes in the following days will be required.
Bettas do rely on their gills more so than the labyrinth organ, so if you see them gulping for air at the surface more often than normal, there are three likely causes. The first is oxygen deprivation, which is the least likely one and hardest to test for. The second is ammonia poisoning, and the third is nitrite poisoning.
Ammonia and nitrite poisoning are very common, and often fatal, issues that new fish keepers encounter. Most go into a pet store and buy a betta, and hopefully a 5-gallon tank with a heater and filter, then go put it all together. The issue with this is that there was no cycling period, which takes about a month with a proper ammonia source.
Ammonia causes severe burns all over a fish and often causes serious gill damage. Nitrite binds to hemoglobin in the blood and prevents it from carrying oxygen, suffocating the fish. Red gills and gasping are signs of both types of poisoning. These two conditions are best treated with daily water changes to remove all traces of ammonia and nitrite.
Unfortunately, oxygen deprivation also has these symptoms. Although you can buy a test to determine the oxygen levels, it is easier and cheaper to test ammonia and nitrite. If you don’t have any ammonia or nitrite, your fish has not been trained to only eat from the surface or blow bubbles, and your betta is not making a bubble nest, you should consider oxygen deprivation as a potential cause.
In conclusion, betta fish do need oxygen, both from the water and from the atmosphere. Even though warm water has a lower dissolved oxygen content, you do not need to add a bubbler or increase surface agitation unless your betta has a friend.