Do Goldfish Need A Filter In The Tank?

Do Goldfish Need A Filter? Featured image of fancy goldfish

Time to put this question to bed, do goldfish need a filter in the tank?

A lot of new goldfish keepers believe that you don’t need a filter for a little goldfish tank. A lot of keepers believe that a goldfish can be put in a small tank, filled with water and voila…

Check out my sweet new tank!

This is definitely the wrong way to start a new goldfish tank!

How healthy you keep your fish and their environment will determine how long you will have them around. On average, a goldfish has a lifespan of between 15 and 20 years. However, this only applies to a healthy fish, that live in the right environment and that are fed on the right food. A goldfish that is unhealthy or that lives in an unhealthy environment may have its lifespan reduced to as low as 24 hours.

Let’s look at why filters are important and this will help us answer the “Do goldfish need a filter” question.

Why Should You Install A Filter On Any Type Of Aquarium?

Most people who keep tropical fish will just assume that a filter is necessary but for goldfish (also a freshwater fish) we expect them to clean their own tank. You need to remember that there is no Mrs. Doubtfire in the goldfish world.

That means that unless there is a filter in the tank your goldfish will be swimming around in their own poop!

Would you like to swim in your own poop?

That is not all that is found in your aquarium though. The water also contains food particles, free-floating particle matter, and dangerous chemicals. If this waste is not removed you are putting your fish in great danger.

Chemistry lesson coming up…

When fish waste is concentrated in water it will cause water toxicity. When the toxins build to high levels, the water that the fish live in will become poisonous to the fish inside. All fish tanks have ammonia but at low levels, this will not be a problem. As levels start to increase ammonia stress will kick in. At this stage, the fish may show some symptoms of weakness and fatigue. Early intervention may help save their lives.

If the levels get higher they will reach the fatal stage known as ammonia poisoning. At this stage, the fish have got little to no chance of surviving.

Installing a filter on any type of aquarium will help keep waste to a minimum and this means happier and healthier fish.

What Is The Nitrogen Cycle

If you want to keep happy fish in a healthy environment you have to understand the nitrogen cycle.

The nitrogen cycle basically refers to the process through which bacteria converts harmful wastes into harmless substances. In the natural environment of the fish, the ecosystem takes control of all the processes in the cycle. However, in an aquarium environment, it is the duty of the fish owner to facilitate the cycle. The nitrogen cycle happens in 4 steps:

Step One: The decay of waste products i.e fish waste, plants, food wastes, dead animals and so on. This process leads to the production of ammonia- which is highly toxic to fish when levels get out the safe zone.

Step Two: A bacteria known as Nitrosomonas converts the ammonia into nitrite. Nitrite is toxic (it will prevent the fish’s blood from carrying oxygen), however, it is less toxic to fish when compared to ammonia. Fish can actually withstand twice the amount of nitrites compared to ammonia.

Step Three: This stage involves the conversion of nitrite to a bacteria known as Nitrobacter into nitrate. Nitrate is also toxic but less toxic than nitrite.

Step Four: Nitrate is converted into the harmless nitrogen gas under aerobic conditions. This is where your work as the fish owner becomes vital. The aerobic conditions are not provided in the aquarium environment. Therefore, it is super important to keep changing water to dilute the nitrate.

When you buy a new aquarium, you need to start the nitrogen cycle. A new tank lacks all the bacteria that is necessary to start the nitrogen cycle. This will lead to what is known as ammonia spike. This means once the fish starts producing waste, the aquarium will be filled with decomposing matter creating high levels of ammonia.

The increase in the amount of ammonia will lead to the growth Nitrosomonas. The growth of Nitrosomonas, in turn, will lead to the production of nitrites. The continuous production of nitrites will, on the other hand, cause a nitrite spike while reducing the amounts of ammonia.

The nitrite spike will lead to the growth of Nitrobacter bacteria. The Nitrobacter will consume the nitrite converting it to nitrate. When the nitrate levels start rising, you should moderate by adding small amounts of water to the tank regularly.

The nitrogen cycle may last up to 12 weeks. This is why I recommend that you check your water before you add fish.

What Does The Filter Actually Do?

So now you know what is actually happening around your little fish, let’s look at what a filter can actually do for your tank environment. It is more than a neat little water feature.

For this post, I am going to use a hang on back filter to give an example. If you want to learn about the different types of filters available check out the article I wrote about the best fish tank filters.

Image of the AquaClear 70 review

The sole goal of the filter is to remove excess food, decaying organic matter, free-floating particulate, dangerous chemicals, and the fish’s waste products from the water. It starts by taking water from the tank, it then runs it through the filter media and then replaces the filtered water.

Each filter will have a speed at which it works. For a goldfish tank, you want to get a filter that will cycle through the tank 10 times per hour. So for a 40-gallon tank, you would need a filter that can handle 400 gallons per hour (gph). This is normally printed on the box to make it easier to select the right one.

The EHEIM Classic 250 is a great filter for goldfish.

Inside the filter, you need to have some sort of media. This could be a filter cartridge or maybe some filter floss and ceramic rings. To adequately filter the tank you need a mechanical component and a biological component. You may add some activated carbon which would add a chemical component to the filter.

When the water is sucked up into the filter it will go through the mechanical component of the filtration process. At this stage, the filter will catch all the debris and waste from the water. The water will then flow through the biological filter media.

The job of the biological component is to house your good bacteria. This good bacteria colony will help break down the ammonia and nitrites in the water.

If your filter has activated carbon then it has a chemical component. This will remove impurities from the tank. Carbon will only absorb so much and then just becomes a part of the biological filtration. So you will need to replace it about every 3-4 weeks.

Do Goldfish Need A Filter – The Answers Revealed!

There is no doubt that you need a filter for your goldfish tank. Goldfish are heavy waste producers and there is no way you could keep up with manual water changes. Installing a filter will help keep the waste in the water to a minimum.

That is not all though, your filter is a place to house the good bacteria that will keep the bad bacteria at bay and reduce your ammonia levels.

For superior filtration a canister filter is the best option in my opinion. Check out: The Best Canister Filters

If you want a low maintenance tank then goldfish are not the best choice. Do you really know how big a tank goldfish need?

They need a big tank of at least 40 gallons for a common goldfish and at least a 20 gallon tank for one fancy goldfish. As for the filter, for commons it will need to be capable of pulling 400 gph to successfully filter the water.

Do you have a filter for your goldfish tank?



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