Round fish tanks began to become popular years ago due to their multiple appearances in movies and television series. Hollywood brought us home the possibility of having in our room a small round fish tank with which to enter the world of cold-water fish.


Although they are called round fish tanks, the truth is that this type of aquarium does not always have a perfect ball or sphere shape. The common feature of all of them is an opening at the top through which to access their interior. A key opening for feeding fish or carrying out maintenance tasks. These fish tanks usually have a capacity of between 5 and 15 liters and in most cases are made of glass. Although round fish tanks can seem like a great decorative element, they are very harmful to fish for various reasons.

Round fish tanks are bad or good for fish

There is a lot of controversy around the round fish tanks. Over the last few years, several very defined sides have been generated. For and against this type of fish tanks. In this section, we will discuss the reasons why round fish tanks are bad for fish explaining all the disadvantages they have with respect to a “conventional” aquarium and, more importantly, their effects on fish.

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The great disadvantage of round fish tanks or ball tanks is that, due to their characteristic shape, they make it practically impossible to install technical devices. Or at least, that they can be placed properly. We refer to heaters and filters. This limits and much, the chances that the water is in optimal condition for the fish. Now, as we will see later, there are some exceptions in the market.

If a round fish tank cannot count on a water filter, the water cannot be kept free of impurities, debris and harmful substances. In addition, we must bear in mind that the vast majority of filters generate a movement and flow of water that creates currents and provides greater oxygenation.

As for the size, round fish tanks usually have a capacity of between 5 and 15 liters. This is a great limitation to be able to keep in optimal conditions a cold water fish (the fish that are typically kept in round fish tanks). Cold-water fish, also called goldfish, require at least 45/50 liters per specimen. And what is equally important, it is recommended to keep them in groups.

On the other hand, and directly linked to the point mentioned above, by their shape, round fish tanks do not offer much space for swimming and forces the fish to move in circles. This can negatively affect your mood and behavior. In addition, the design of these fish tanks causes the vision to be distorted, both that of the fish on the outside and ours when it comes to observing what is inside. Its spherical shape is decisive in this aspect.

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Round fish tanks are usually made of glass. Therefore, when carrying out maintenance tasks such as cleaning, extreme precautions must be taken to prevent them from being damaged. Due to their shape, they must be placed somewhere where sunlight does not directly affect it, since it can enhance the sun’s rays directly affecting the temperature of the water.

Which fish can live in a round fish tank

Once the disadvantages of round fish tanks have become clear, if we finally venture to install an aquarium of this nature, what types of fish can live in round fish tanks? Well, based on the limitations described above, the most suitable thing is to opt for very resistant fish. The Betta splendens are a very interesting option. They will be able to live in a fish tank of this nature, although their quality of life will be much worse than if we keep them in a conventional aquarium with all the equipment (heater, filter and air pump).

Round fish tanks with filter and LED lighting, is it possible?

Is there the possibility of having a round fish tank that includes a filtering and lighting system? The truth is that, despite all the drawbacks that we have been listed throughout this text, in recent times some other manufacturer has shown that it is possible to have a fish tank of this nature with solvent equipment. In the catalog of aquariums of firms of the stature of TETRA, there are round fish tanks with filter and LED lighting.

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However, since a round fish tank has such equipment, it will still not be the most suitable place to keep fish. However, and having controlled parameters such as temperature and having a filtering system, we can be facing an ideal alternative to traditional shrimp or nano aquariums.