Can You Over Filter a Fish Tank?

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Among the most critical factors that will make or break a fish tank setup is filtration.

You often hear about filters not being effective enough, but can you over filter a fish tank? What happens if you go overboard?

To ensure the safety of your pet fish, we’ll talk about the positive and negative effects of over-filtering.

Before all that, though, let’s go back to the basics. What roles do filters play in a fish tank?

Why Are Filters Important for Fish Tanks?

Even if you are a complete newbie to the fishkeeping hobby, you know that a filter is necessary for your build.

It helps cycle the tank, ensuring your fish is not only able to survive but, more importantly, thrive.

A fish tank filter removes dirt and debris from the water and removes nitrate and ammonia buildup that can harm your fish.

In addition, it helps aerate the water so that your fish and its friends can breathe.

Unless you want an aquarium full of sickly or, worse, dead fish, you must install a tank filter according to the size of your aquarium.

With how busy life can get, no one has the time to do weekly water changes. A tank filter helps extend the interval between tank cleaning.

That said, it doesn’t mean it won’t require maintenance altogether. Even with a filter, you still need to do water changes.

Moreover, you have to check the filtration system from time to time to make sure it does not clog.

Different Types of Fish Tank Filters

You will find different filtration systems, but mechanical and biological filters are the most common.


If you don’t address increasing nitrite and ammonia levels in your fish tank, it will soon reach dangerous levels.

However, with the right bio-filters, you can rest assured these waste products are broken down and become harmless.

This is all possible through the use of beneficial bacteria.

The end result is nitrates, which your live aquarium plants can get nutrition from to grow and thrive.

If you don’t plan on adding live plants, you can use another type of filter to remove nitrates from the water—mechanical filters.


Mechanical tank filters make use of sponge and floss pads to remove algae, fish waste, and other impurities from the water.

This type of filter runs via an electrical air pump.

Basically, the dirty aquarium water gets sucked through the tubes and then passes through a physical filter to remove debris.

This first step only removes larger particles, like uneaten fish food.

As such, the water then gets sent through a biological media, breaking down nitrites and ammonia.

Lastly, it will flow through a type of fine chemical filtration system to filter out any impurities left.

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Can You Over Filter a Fish Tank?

Over time and because of various factors, algae blooms and bacteria buildup can become visible, ruining the beauty of your build.

If that’s the case, is it safe to assume that using two or more filters is better?

While it’s possible to achieve a healthier bio-flora from twice as much filtration, it’s not always that straightforward.

Using the right kinds of filters, over-filtering should not harm your fish.

However, you have to ensure they don’t create a strong or too powerful current that could stress out your tank inhabitants.

What does over-filtering even mean?

Over-filtering happens when the aquarium filters you set up create a current that is too strong for your fish.

It’s a far too common mistake that beginners make, so it will benefit your fish if you pay close attention.

The most obvious reasons for over-filtering are too much dirt in the filter or using a high-powered pump that does not match your tank size.

Effects of Over-filtering Your Fish Tank

Plants control the aquarium’s carbon and nitrogen levels, and microorganisms support the overall healthy environment in the tank.

If you don’t allow your setup to cycle before adding anything in, don’t expect good results.

That said, cycling can only happen if you have a good enough fish tank filter.

On the other hand, here’s what will happen if you overdo it:

  • There will not be enough healthy bacteria in the tank.

Again, tanks must cycle and produce beneficial bacteria to achieve enough balance for fish to survive.

Unfortunately, it won’t happen if the water in the tank is moving too quickly. As a result, you might see algae taking up every inch of your tank.

  • It can stress out your fish.

Fish can experience stress, too. In fact, there are numerous health issues that could result from too much stress.

By putting in too many filters than necessary, your fish can develop several diseases.

  • Seeing anything in the tank could be challenging.

Over-filtering a tank can mean it will be harder to see what’s happening inside. Your vision could be clouded by bubbling water.

A too powerful current can also scatter ornaments and unroot newly planted live aquarium plants.

  • Strong currents might be uncomfortable or dangerous for some fish.

You will know that a filter is too powerful relative to the size of your tank when your fish consistently swim too close to the ground.

The same can be said if you find them always hiding and refusing to leave their safe spot.

Basically, if your fish is moving too quickly, that means they are having a hard time to relax.

  • A fish tank with not enough bio-filtration and cleaning needs more filtration.

You may require an additional line of filtration if none of the natural filters previously mentioned are present.

If you utilize this technique, you can add more filtering by using a secondary pump that is a little weaker.

  • If one of them breaks, you will always have a backup filter.

On a positive note, setting up two or more filters in your tank means you get a backup even if one of them malfunctions.

In case you don’t know, some fish won’t survive the night without a filter, so this could be a very serious concern for some fishkeepers.

  • Reduced contact time of bacteria with the water.

Another advantage of over-filtering is that it reduces bacteria buildup in the water twice as much.

An aquarium’s bio flora needs to be balanced. With more than one filter installed, there’d be fewer bacteria in the tank to possibly harm your fish.

  • It can move the water too much for comfort.

When it comes to setting up an aquarium filter, the goal is to achieve the perfect balance.

Unfortunately, you won’t achieve this balance if the water cycles too quickly. In general, the water should go through the filter just four times an hour.

Pay Attention to the Current

So, can you over filter a fish tank?

As you can see, there are pros and cons to having more than one filter in your fish tank. However, it doesn’t mean that over-filtering is a good idea.

In the end, what you should aim for is a filter that doesn’t create too much movement in the water.

Otherwise, your fish can get too stressed and develop infections and diseases.

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