Do Goldfish Need A Filter? (Everything You Need To Know!)

How many times have you seen a goldfish in a tiny bowl with no filter and minimal decorations? Everyone knows that goldfish are hardy, so it begs the question, “do goldfish need a filter?”

In this article, not only are you going to find out whether goldfish need a filter, but you’ll also learn about the benefits of having a filter, the different types of filters, and what to do when you don’t have a filter; and more!

So keep reading to find out everything you need to know!

Do Goldfish Need A Filter?

Filters are one of the most important pieces of equipment for a goldfish tank, and to ensure that your goldfish is happy and healthy, you should definitely have one.

Goldfish are particularly messy fish, so the water quality can become bad very quickly if it’s not looked after. While some people do get by without a filter in their goldfish tank, the chances are that their goldfish are going to suffer, and their lifespan will probably be reduced dramatically.

So if you’re going to get a goldfish, make sure you add a filter to their tank as well!

What Do Filters Do?

Standard filters have three different types of filtration media that keep the tank clean. These are biological filtration, chemical filtration, and mechanical filtration. Here’s a brief guide on what each one of them does and why they’re essential for a tank.

Mechanical Filtration

Mechanical filter media is the first stage of filtration that the tank water will go through. During this time, larger pieces of debris and waste are removed from the tank and stay in the mechanical filter until it’s cleaned.

Mechanical filtration looks very similar to a sponge, and it needs to have bigger holes to catch bigger debris while still letting water pass through unhindered. Once the water has passed through the mechanical filtration, it then moves to the second part of the filter system.

Chemical Filtration

Chemical filtration is the stage any chemicals that shouldn’t be in the tank are removed. This is a great way to stop your goldfish from becoming accidentally poisoned by something that shouldn’t be in the tank.

On top of this, another benefit of chemical filtration is that it removes any discoloration from the water as well as bad odors. If you need to medicate your goldfish, it’s best to remove the chemical filtration; otherwise, it can stop the medicine from working properly.

There are many different types of chemical filter media available; however, the most commonly used one is activated charcoal.

Biological Filtration

This is the final stage of filtration (and arguably the most essential). Biological filter media is where beneficial bacteria in your tank are going to live. When the water passes through the biological filter, the bacteria will feed on any ammonia, nitrites, and nitrates, removing them from the tank.

This is essential for goldfish; without them being removed, your goldfish will become incredibly sick and, in a lot of cases, die. Essentially they’ll be swimming in and breathing poison.

While this beneficial bacteria can be found around the tank, such as in the gravel and on plants, it’s not going to get as much water passing over it like the bacteria in the filter.

(As well as a heater, you also need to consider getting your goldfish an air pump and heater.)

What Are The Benefits Of A Filter?

Now you know what a filter does, it’s also important to know its benefits. Here are the main benefits you’re going to get from using a filter in your tank.

You Won’t Have To Change The Water As Often

The first biggest benefit to you is that you’re not going to have to change the water as often. When you don’t have a filter in your tank, it’s not uncommon to need to change the water every 2-3 days. This can quickly become time-consuming and tedious to you, not to mention the fact it’s going to stress your goldfish out.

When you’re constantly adding and removing water from the tank, the act itself is going to stress your goldfish, but other things will as well. For example, the constant changes in water parameters when you add tap water are also going to affect their immune system.

The Water Will Look Cleaner

And of course, the second biggest benefit to you is that the water is going to look cleaner for longer. Every time you perform a water change, you’re going to kick up a lot of dirt from the bottom of the tank, which makes the tank cloudy.

On top of this, a filter also helps to remove dirt, so even when you do kick it up, there’s going to be less of it. In fact, you can even get water polishers, and other filter media other than the three mentioned to help keep the tank looking cleaner as well.

Your Fish Will Stay Healthier Longer

You know that filters remove all the bad stuff from the water that shouldn’t be there. Ammonia, for example, is going to directly make your fish sick if the levels are too high.

But it’s not just this. When there’s too much waste in your tank, bacteria, parasites, and fungus are going to have the perfect conditions to breed in. This means your goldfish is going to be a lot more susceptible to getting sick.

This is particularly true with goldfish, which are messier than a lot of other fish. If you’re not making sure that the water is staying clean, then the chances of them getting sick are going to increase massively, no matter how healthy they are.

Increases The Amount Of Oxygen In A Tank

Lastly, if a filter is running in your tank, then it’s going to increase the amount of oxygen in the tank as well. This is because it will agitate the surface of the water, which is essential for the gas exchange of carbon dioxide and oxygen. In short, it helps carbon dioxide leave the water and oxygen enter the water.

Without this, your goldfish may find it harder to breathe.

(If you’re keeping other fish, then they may need a filter as well. Find out whether you should keep a filter in a guppy tank.)

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Different Filters You Can Use In A Goldfish Tank

There are lots of different filters you can use for your goldfish tank, and the type of filter you choose really depends on the size of the tank.

Any filter you’re going to choose will have its pros and cons, so you’ll need to decide what’s best for your tank based on your individual circumstance.

Here are the main types of filters to choose from.

Canister Filters

Canister filters are often best for bigger tanks, and if you’re going to be keeping goldfish, you’re going to need a big tank. They are placed below the tank, where the pressure of the water helps it to circulate dirty water and turn it into clean water.

Another great benefit of canister filters is that they’re easier to clean because they’re outside the tank. You don’t have to worry about removing them from the tank and getting everything wet. In fact, most canister filters are designed in a way to keep mess to a minimum.

HOB Filters

Another great choice for a lot of tanks is HOB filters. These are filters that hang on the back of your tank, so they don’t take up nearly as much space. While they’re normally used for smaller aquariums, there are still ones that are big enough for larger aquariums too.

While they don’t offer as many benefits as canister filters, they’re normally a little bit cheaper, so if you’re getting a filter on a budget, you can normally find a good deal with HOB filters.

Internal Filters

These filters can be found inside tanks, as you can guess from their name. They normally come as part of an aquarium kit; however, it is possible to purchase them separately.

The biggest downside with internal filters is that they take up space in the tank and can often be unsightly. As well as this, you can often splash a lot more when you’re trying to clean them.

Undergravel Filters

While undergravel filters aren’t as common as other filters, it doesn’t mean you should write them off altogether. Undergravel filters use the gravel in your tank as the mechanical filter, and the chemical and biological filters are often housed in tubes nearby.

However, undergravel filters are extremely hard to set up when if you’ve already got an established tank. As well as this, some areas of the gravel tend to have more suction than others which means debris can build up in certain areas.

(Have you ever thought about keeping your goldfish with mollies or guppies?)

What To Do If You Don’t Have A Filter

If you don’t have a filter, then there are things you can do to reduce the chance of your goldfish becoming sick. However, all of these are only temporary solutions, and it’s still best to get a filter for your tank ASAP.

Perform More Water Changes & Keep The Tank Clean

The best thing you can do is perform more water changes, as well as keeping the tank clean. You can do this in a couple of ways. The first and most important thing is obviously removing some water every day and replacing it with new conditioned water.

As well as that, you should also disturb the gravel and vacuum it to make sure that you’re removing any waste and debris that may have sunk to the bottom. You should also remove any uneaten food which will begin to decay if your goldfish doesn’t eat it.

Test The Water And Use Ammonia Neutralizers

You should also be testing the ammonia, nitrite, and nitrate levels in the tank to make sure that they’re not too high. (If you haven’t got a test kit, then I highly recommend the API Master Test Kit.)

If the ammonia is too high, then you should use an ammonia neutralizer such as API Ammo Lock. This will detoxify the ammonia, making it harmless to your goldfish, but it will still be able to feed your beneficial bacteria.

Add More Plants

Adding lots of plants to the tank is going to help it clean. Plants feed on all the waste of fish, which is going to keep the ammonia levels low. As well as this, they also produce oxygen which beneficial bacteria need, they create a place for beneficial bacteria to live, and they also remove carbon dioxide.

If you’re not sure what plants to start with, java fern and anubias nana are a great choice.

Don’t Overstock The Tank

And, of course, make sure you’re not overstocking the tank. When you overstock the tank, the ammonia inside it will build up a lot faster. As well as this, the waste from all the fish is going to create the perfect breeding ground for bacteria and parasites.


So as you can see, filters are an essential piece of equipment for the health and happiness of your goldfish. If you haven’t gotten a filter yet, then you should definitely invest in one, and if you’re not sure what type of filter, then canister filters are probably your best bet for a goldfish tank.

About the author

Hey! I'm Antonio!

Betta fish keeper for over 6 years now! Since owning a betta I've also housed all kinds of tropical fish, and have seen all manner of problems and how to look after them!

If you need any advice you can always message me or better yet join the Facebook group where a community can answer your questions!