Does a Fish Tank Need a Filter?

If you are planning to get a fish tank or aquarium at home, then there are many things you need to put in place before you get the fish. Of course, you need a fish tank. You may have a question whether you need fish tank filter.

This guide explains the answer to your question. You can also learn about the uses of having a filter and what would happen if there is no filter. Read this comprehensive guide to know all about fish tank filters.

What is a fish tank filter?

A fish tank filter helps to keep your fish tank clean. It filters or removes waste from the fish tank. Leftover food particles, decaying organic matter, waste from the fish, and any other particles are removed from the fish tank by the filter.

There are three types of filters – biological, mechanical, and chemical.

1. Biological filter

A biological filter removes biological waste from the fish tank. Microorganisms in the tank breakdown down the waste from the fish into ammonia and other substances. These can become toxic and must be removed. The toxic ammonia is broken down into nitrate, which is not harmful. Biological filtration is a must. Without it, the ammonia can harm fish and plants kept in the fish tank,

2. Mechanical filter

This is the basic type of filter that traps solid waste particles as well as plant materials. Any food that is not eaten, solid fish poop, and leaves are trapped by mechanical filtration. This helps to keep the fish tank clean. The filter also needs to be cleaned to avoid it from becoming clogged up with waste.

3. Chemical filter

There are various chemicals that could be in your fish tank. These chemicals can be harmful for your fish. A chemical filter will ensure all such chemicals are filtered out from the tank. A filter made of activated carbon is usually installed. This helps to get rid of chemicals easily. The filter needs to be changed once every couple of months.

Importance of fish tank filters

Filters are very important for a fish tank to ensure the fish remain healthy, and the tank remains clean. Of the three types of filters, a biological filter is a must. You may not face many problems if you don’t have a mechanical filter. You can clean the tank manually. But a biological filter is vital since it removes toxic ammonia from the tank.

The importance of fish tank filters and fish pond filters explained by the various benefits they offer:

  • The filter helps to keep the fish tank clean that allows you fish to thrive. It keeps the tank clear, so you can get a clear view of the fish.
  • Stagnant water is avoided when you use a fish tank filter. Stagnant water can be harmful for fish.
  • Solid waste, whether it is fish poop, plant debris, or any other particulate matter is removed when a fish tank filter is used.
  • Toxic chemicals can be removed from the water ensuring it is safe for fish.
  • A filter ensures good bacteria lives in the fish tank. This good bacteria allows fish and plants to thrive.

What happens if you don’t have a fish tank filter?


If your fish tank does not have a filter, the result would be a dirty and unclean fish tank. Such a tank would make it difficult for your fish and other plants in the tank to survive. A dirty tank would have cloudy water that would disturb your view of the fish. In such a situation, you would need to manually change water frequently.

The biggest problem if you don’t have a filter is the risk to the lives of the fish. The fish waste produces ammonia and nitrite. A filter will convert these to harmless nitrite. In the absence of a filter, the ammonia and nitrite can kill your fish.

When a tank is not filtered or if the water is not changed, then the ammonia levels begin to increase. This causes ammonia poisoning that make it difficult for the fish to breathe. They become lethargic and do not move around in the tank. The gills may change color to purple or blood patches may be seen. Ultimately, the fish would die.

A filter offers two benefits. Firstly, it breaks down ammonia. Secondly, it allows good bacteria to thrive. The good bacteria ensures the nitrogen cycle is maintained that leads to lesser ammonia in the tank.

Getting a fish tank filter

You need to get a good quality fish tank filter to ensure your fish are healthy and do well. There are different kinds of filters you can get. Here are 3 common types that you can choose from:

1. Sponge filter

In this type, a spongy material is placed at the bottom of the tank. Debris from the tank is sucked out through the filter’s air pump, which is located outside the tank. The debris is removed through the sponge placed in the tank. This is ideal for small tanks with fewer fish.

2. Canister filter

This is a powerful filter that is placed below the tank and is hidden. These tanks are best suited for large tanks containing many fish. These powerful filters have pipes that suck out debris and other waste and send in filtered water. They are a bit expensive but do their work well.

3. HOB filter

A HOB filter or a hang-on-back filter is hung at the edge of the back of the tank. It sucks out water from the tank and send it to the filter where all waste and chemicals are removed. The filtered water than is sent back into the tank. This filter is preferred by both hobbyists and experienced fish tank owners. It can be used in small tanks as well as bigger ones.

When buying a filter tank, you need to consider the flow rate. This is the rate at which water flows through the filter and is measured in GPH or gallons per hour. The filter GPH should be around four to six times the total volume of the fish tank.