Do Fish Tanks Need a Filter? It Depends ...


Do fish tanks need a filter - a question that comes to every person who is into fish-keeping as a hobby. The community is divided with varying opinions; some say it is necessary while others say it's not.

But, what's the actual answer? Do fish tanks need a filter?

do fish tank needs a filter 1

Before you know if your fish tank needs a filter, you need to understand the ecosystem inside the tank, and the purpose of the filtration system.

The factors

Filtration in water bodies

Any space comprising of living organisms will generate waste. And, for sustaining life in the concerned space, it is vital that these waste products are removed from the biosphere. That said, natural water bodies have a system in place for removing the pollutants released by the aquatic organisms.

nitrogen cycle in water3 1 Image Source: Fluval Aquatics

In natural water reserves like lakes, rivers, and seas, biological filtration keeps the aquatic environment suitable for the fishes. The system breaks down the harmful ammonia waste into nitrites and nitrates which are further utilized by the organisms in the water body.

This filtration system is not available in your fish aquarium. Meaning, after a certain amount of time, there will be the accumulation of waste products. This accumulation of waste products changes the water conditions, thus, posing a risk to your fish lives.

Tank conditions

The aquarium water remains the same until you change it. Between every water change, the water collects various impurities and wastes from the fishes. Thus, the water quality keeps deteriorating until you clean or replace the water in the tank.

If you have a small tank (which we do not recommend for any beginner), any changes in water conditions due to this waste collection will be fast and drastic, thus, limiting your time to mitigate any problem. And before you can do something, your fishes die.

The same applies when hosting a large school of fishes. A large fish population will generate more waste. So, if you are hosting a large number of fishes in a tank, the frequency of filtration or cleaning the tank will be higher when compared to a situation where you are hosting a smaller school of fishes.

Type of fish

Some species like Betta fish can survive without filtration system while others will need a filtration setup. It also means that some fishes are more adaptable to their surroundings than other species. So, whether a filtration system is required partly depends on the type of fish you intend to host.

Purpose of filter in an aquarium

The primary goal of a filter is to maintain suitable and stable water conditions within the aquarium tank by removing the impurities from the tank water. What happens automatically in nature requires a system in the aquarium setup.

Filtration systems for aquariums work in three ways - chemical, mechanical or biological.

  • Chemical filtration setup deals with the breakdown of harmful substances in water with the help of catalysts (like carbon).
  • Mechanical filtration setup works on the simple process of separating elements based on the difference in sizes.
  • Biological filtration setup promotes the growth of good bacteria which helps breakdown the waste products into harmless substances.

biological filtration 1

You might argue what if you manually clean the water regularly? After all, that's what a filter does. It conditions the aquarium water, making it suitable for fishes to live in.

Yes, you could perform regular cleaning of aquarium water, but there are some problems.

First, it will be time-consuming and requires more work. You might decide that you are good with manual water treatment and do not need a filter. But the thing is, slowly but surely, you will grow tired of the routine work when the initial excitement of fish-keeping dies. You will have to perform the cleaning task repetitively within a short time (say, thrice a week) which would not be convenient.

Second, manual water cleaning will disturb the system inside the tank. Fishes will be shocked due to your intervention. They need a stable water condition to live healthily; constantly cleaning or changing water alters the water condition which is not ideal for your fishes.

However, you could get away without using a filter in cases where you have a large tank with a tiny fish population. The most common example is a fishbowl setup. Goldfishes are the most popular choices for bowl setups. In such cases, you are habituating a few fishes (say two or three) in a large water volume. The waste generated will be meager when compared to the large water volume, meaning magnitude of change in water conditions is less.


Irrespective of where they reside, fishes need a suitable environment to survive. In water bodies, the appropriate conditions are maintained by natural filtration processes. This feature is not available in your aquarium. Hence, you need to do either of the two things: clean the water regularly or install a filtration system that does the job.

Manual cleaning will mean frequent change in surroundings which is not good for your fishes. On the other hand, filtration systems work automatically without your intervention. With a filtration system in place, you are only responsible with the task of water changes and not cleaning. Also, fishes are at ease due to stable environmental conditions.

fishes in aquarium 1 Image:

What we suggest is if you have a considerable fish population, opt for a filtration system. It will provide you with some headroom for errors in your fish-keeping experience. You will be free from continually maintaining suitable water conditions and only be required for occasional tank cleaning.
Alternatively, if you are dealing with a single or pair of fishes, you can skip over filters until you keep the water at least three times the required volume of each fish. Here are a list of fishes that can do without a filtration setup.

So there's your answer. We hope this article helped you with your query.

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