It’s almost a cardinal rule in the fish keeping hobby to have a good filtration system running to keep the fish healthy and alive at all times. At the same time, there will always be exceptions to such rules. As hard to believe as it is, there are some fishes of fish that could thrive for long periods of time without the use of conventional aquarium filtration systems.
Before anything else, a disclaimer; Fishes, like all living things, need oxygen to survive. Furthermore, prolonged exposure to toxic ammonia, nitrates and nitrites could endanger the health and well-being of any fish. However, through years and years of evolution and adaptation, by biological and/or physiological design, some fish are able to thrive in environments some others cannot survive. Today, we will discuss fishes that could thrive without filtration systems. However, please note that we would still have to recommend keeping a good filtration to provide healthier living conditions for the fish.
Is it really possible? Well, according an article written by National Geographic, there are fish that have evolved to sustain life even outside of water. These fish, have either stayed the same or have evolved throughout the years. Either way these fishes have developed the ability to breathe from the air outside of the water and in environments other fish would not be able to.
For us to know what fish could thrive in an aquarium without a filtration system, first, we need to know what a system does. Generally, most filtration system works both mechanically and biologically. The mechanical part takes solid waste and keeps them out of the tank by trapping them in less permissive media such as polyester wool. On the other hand, the biological side converts toxic byproducts of decay to less toxic chemicals. These byproducts being ammonia, nitrite and nitrate. While ammonia and nitrite is extremely toxic to fishes, nitrate, the byproduct of the nitrogen cycle is only toxic to fish upon exposure to very high amounts in long periods of time. Lastly, the movement created through the filtration system also gives crucial oxygen in the water in order for the fish to be able to breathe.
Now what kind of fish will be able to survive tanks without filters? We have two main characteristics that would help us narrow down which fish could survive such environments. These are the following:
- Biological adaptation/evolution
- Overall hardiness
Adaptation/Evolution
Biological adaptation and/or evolution, as mentioned a while ago, gives some fishes a coping mechanism in order to survive in an environment where what a filter does is not present. These changes in the fishes’ physiology and/or biology may come in the form of them being able to breathe from the surface or their bodies being able to produce mucus to shield them from the toxicity of some chemicals.
Overall hardiness
Aside from being able to adapt well to different environments, since aquarium tanks without filtration are generally not suitable environments for fish to thrive in, fishes that we are looking for must be able to handle such stress. Hence, they should be more hardy and tolerant of such environments than other fish.
Now that we have narrowed down our search by knowing what would be the cause of not having a filter and by using our two main characteristics a fish should have, here are the survivors!
Gourami
An Anabantoid or more commonly know as labyrinth fish the many different kinds of Gouramis have evolved to be able to breathe air from the surface of the water. They do this through the help of their labyrinth organ which takes oxygen from the surface of the water to their bloodstream. Without dissolved oxygen, which is another byproduct of a filter, a fish will usually die. However, with the presence of its labyrinth organ the Gourami will be able to survive.
Also, Gouramis are known to be very hardy. They are amongst the fish that are recommended for beginners. Indeed, Gouramis have a good chance of surviving waters without filtration.
Betta
Yet another Anabamtoid or Labyrinth fish, the Betta or more famously known as the Fighting Fish, is like the Gourami because it could also breathe through taking air from the surface of the water.
What makes the Betta more suitable to aquarium without filter is how they are bred and kept. For decades, Bettas have been bred and kept in very small tanks tanks without filtration. Because of this, the Betta might have already adapted to conditions wherein the benefits of a filtration system are not present.
Lastly, as a mostly solidary fish, its lack of tolerance of fish of the same kind makes it less likely to be kept with other fish. Since it is alone, it would produce less waste than a normal small community of fish. With less fish comes less waste and a lesser need for a filtration system naturally follows.
Mudskipper
These species of gobies are one of the most unique fishes in the entire animal kingdom. They are considered as “amphibious fishes” due to their ability to thrive outside of water. As a matter of fact, mudskippers are known to spend parts of their days outside of water. They are able to do this through their skin and their mouth like most amphibians. However, they need to be moist to be able to do this.
This extreme adaptability to thrive on both land and water also gives the mudskipper extreme hardiness since they are able to tolerate such conditions. Thus, the Mudskipper is one fish that could thrive in tanks without filters.
Lungfish
If there’s one fish that we’d bet on surviving tanks without filters, it is the mighty Lungfish! Lungfish, as their name suggests, have very complex lungs that enable them to breathe air and get oxygen even when not underwater. This complex characteristic of the Lungfish enables them to survive months outside of the water.
They are also able to cover their body with mucus for protection especially in times of drought when they burrow themselves under thick mud. This mucus membrane could also serve as their food for such times of hibernation since they are able to consume them while they slow down their metabolism.
Lastly, the most important yet interesting thing about lungfish is that this characteristic have been present for thousands of years. Hence, as weird as it seems, perhaps it is the lack of evolution that enables the lungfish to survive such dire environments. They are extremely hardy since they have remained unchanged for thousands of years. Indeed, the Lungfish is the ultimate Unfiltered-SURVIVOR!