How To Keep a Fish Tank Clean Without a Filter

Even though fish can seem to be an easy pet to own, there are still many expenses that go into ensuring proper care and good quality of life. The tank that your fish spends its life in needs to provide everything necessary to survive.

There are a lot of up-front expenses when it comes to getting a fish and all the proper supplies. Generally, filters are considered one of those items imperative to keeping a fish alive and healthy. That being said, it is indeed possible to maintain an aquarium without one. So keep reading to find out how to keep a fish tank clean without a filter.

The Importance of Filtration for Aquatic Pets

Filters are so crucial to the survival of your fish because they keep toxins from building up in the water and causing severe illness or death to the inhabitants.

One of the deadliest toxins in aquariums is a chemical called ammonia. Ammonia naturally occurs in any ecosystem and can be broken down by bacteria. In fish tanks, especially ones that are less than 5 gallons, ammonia can quickly build up and become deadly. That’s one of the reasons it’s so important to keep your fish tank properly cycled.

Ammonia is produced by your fish and the breakdown of their waste, leftover food, and dead organisms in the tank. With proper filtration systems, ammonia is broken down by beneficial bacteria into nitrite, which is less harmful to fish.

The nitrite is then further broken down by bacteria into nitrate, which is entirely harmless to fish.

These beneficial bacteria will naturally populate a tank a few weeks following setup. Most of these bacteria will be concentrated in the filter. Some may reside in the main tank, but not in large enough numbers to keep the water healthy.

Without filtration or frequent water cycling, ammonia levels will become toxic and cause ammonia poisoning, leading to death.

How to Keep a Fish Tank Clean Without a Filter

Even without a filter, you need some method of filtration to keep your fish from dying of ammonia poisoning or suffocating in the water due to too much nitrite. Without the benefit of a filter to concentrate beneficial bacteria, you will have to research and cultivate an ecosystem where these microorganisms can keep up with the amount of ammonia being produced.

This trend is called balanced or natural aquariums.

Balanced Aquariums

These aquarium setups aim to reproduce a natural pond ecosystem in a fish tank. They do not include filters, fertilization, air stones, or water changes (at least not frequently).

But while these aquariums can be entertaining to interact with and watch, they do not support large fish, or many fish, and can be very challenging. 

You can have a variety of organisms in these tank setups, but they aren’t all going to be fish. Some common inhabitants of balanced aquariums include shrimp, small fish, and some types of snails.

The focus of this sort of tank is to create a balanced ecosystem, meaning every organism in the setup is not only compatible but fills its own niche.

In a natural and balanced aquarium, some organisms can decompose waste and debris into nutrients for other organisms. A large amount and variety of plants are necessary to not only absorb nitrite from the water but produce oxygen. Small consumers need to balance the plants and bacteria, and predators will keep small consumers in balance.

Part of creating a balanced tank is building it up instead of adding everything in all at once. An organism needs to be established and thriving before you can add something that preys on it. You may need to be extra attentive to your ecosystem in the first months to ensure everything interacts sustainably.

It can take a lot of research and time to establish an ecosystem that will remain in balance like this. Once established, these ecosystems may still be very delicate. Maintaining the ecosystem will require care and diligence.

If you can perfect this balance, it can be a rewarding thing to behold.

One of the methods for achieving these naturally balanced tanks includes the Walstad method, which has some of the most detailed instructions.

The Basics of Natural Tanks

Some fish hobbyists have developed their methods through intense and thorough research or by accident. But at the core of any of these setups is the base of a planted tank. The concept of which is to essentially have a tank of plants that supports some fish as well.

Natural aquariums do not allow for the introduction of large and colorful fish. It is tough to create an ecosystem capable of supporting shrimp and small fish within the confines of a 30-gallon tank. It would likely be impossible to create a habitat that can naturally support a goldfish within those limitations.

In addition, these tanks may not meet everyone’s standard of cleanliness either. Plants will be well-populated, fish may disturb particles, and beneficial organisms may be found as tiny matter floating in the water. Depending on the setup and methods used, the water could be crystal-clear or somewhat dull-looking.

How To Minimize the Need for a Filter

For most people wanting to maintain a healthy fish tank, some type of filtration is necessary. But it is possible to minimize the use of a filter rather than eliminate it entirely.

Types of Filtration

There are three types of filtration: biological, mechanical, and chemical. Though some claim each is vital to your fish’s health, you do not need all of them.

Filters often lower the frequency you need to perform water changes or cycling, which could be more convenient for some people. They also automate what could be a rather tedious operation.

Biological Filters

The most important type of filter to get is a biological one. Biological filters are the only type that provides a place for beneficial bacteria to concentrate and reproduce. Without a biological filter and sufficient medium for the bacteria to grow, the ammonia levels in the water will quickly become fatal.

The importance of biological filters comes from maintaining that concentration of beneficial bacteria. Excessively cleaning the filter medium can reduce or even prevent healthy amounts of these bacteria from growing.

When cleaning filters, it is essential to be aware of biofloc and biofilm. These brown, gunky substances build up on the filter medium and are often mistaken for mud or waste.

Biofloc is the majority of that goop and is composed entirely of good bacteria. The biofilm is a thin layer on top of the biofloc that forms the entirety of the bacteria that process ammonia and nitrite. 

Both of these substances are necessary for the health of your fish and should not be cleaned off the filter unless they have blocked the flow of water.

Chemical Filters

These are the most unnecessary types of filters for a fish tank. There is often nothing beneficial being done by chemical filters because biological filters already take care of any toxins in the water. 

In addition, the chemicals that are supposed to reduce ammonia levels are not reliable methods of maintaining water quality. Over time, excessive use of these chemicals can also harm the fish and the environment. 

Chemical filtration might only be needed for short-term issues, such as removing medication from the water after it’s served its purpose.

A healthy tank does not need a chemical filter.

Mechanical Filters

Mechanical filters catch any leftover food or other waste that would cloud the water over time. The removal of this debris will also lower the amount of ammonia produced. Mechanical filtration is not as important as biological filtration and may be left out if needed. However, regular cleaning may be to be performed more often.

Minimizing Your Concerns About Filters

If the price is the primary concern, look for a well-rated biological filter that suits the tank size, as this is all you need. Following proper maintenance should keep that filter working for a long time.

You do not need a mechanical filter if you plan on performing weekly water cyclings and manually cleaning any leftover food. Avoiding overfeeding your fish can also reduce the need for a mechanical filter. Keeping up with regular maintenance should reduce the amount of waste building up in the tank as well.

Investing in other creatures that can help clean up waste, such as filter-feeding fish or snails, can also help minimize your need for a mechanical filter.

how to keep a fish tank clean without a filter

Getting a large tank will spread any debris or waste from your fish over more area, which can help the tank stay clean longer.

Start with a smaller number of fish to further reduce the waste produced.


With education, research, time, and dedication, it is possible to set up a fish tank that does not need a filter. However, aquariums without a filter can only support a limited number of fish, and only certain species of aquatic life such as snails, shrimp, and some small fish.

Keep up with the latest aquarium tips and insights!
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