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How to Adjust Flow of an Aquarium Filter

Flow, or you can say flow rate, is the amount of water moving through your aquarium filter per hour. It is essential to the creatures in your aquarium.

Normally, if you have a higher flow rate, the water will move and circulate faster, which will make the water clean and provide a suitable environment for your fish. But you should avoid that the flow is too strong or too weak because it will affect the daily life of your fish.

This article will help you know how to tell and adjust the flow of your aquarium, how to calculate the proper flow and the negative effects of a strong flow. Hope it can help you solve the trouble you meet with the flow while keeping your fish.


How to tell if the flow is too strong or too weak?

Having difficulty in swimming

A strong flow will make it hard for fish to swim. If they go downstream, they will swim with ease, or they will struggle to swim. So when you notice your fish are pushed by the flow, the flow may be abnormal.


Swimming erratically

When your fish are swimming, the normal direction should be straight, if you find they swim at an angle, there may be something wrong with your flow rate. Some diseases may also make your fish swim erratically. Check if your fish are suffering from diseases when you find this phenomenon.


Avoiding the current

When there is something wrong with the current, fish will notice and they will avoid the current area. Some may stay in one spot because it’s difficult for them to swim near the current.


Always hiding behind the decorations

To avoid the current, your fish might always hide behind the decorations in your aquarium. That’s because the decorations can diffuse the flow and make it easier for your fish to swim.


How to reduce the flow of your filter?

Strong flow is more common than weak flow, so this article will explain how to reduce water flow in detail and roughly explain how to speed up flow rate.


1. Reduce from the inlet of your filter

You can change your inlet tubing with a smaller one, then there will be less water flowing into the filter. And the flow will also be reduced when water flows out after being filtered.


2. Reduce from the outlet of your filter

If there is only one outlet of your filter, the water flow will be strong because all of the water flows out through this outlet. If you can create more outlets to diffuse the water, the flow will be reduced. You can also add a baffle to the outlet, then the water will flow out slowly from the filter.


3. Buy a pre-filter

Buy a pre-filter sponge or something similar and wrap the filter. It can maintain a slow-moving environment in the tank and reduce the flow.
pre-filter sponge

4. Add some decorations

Decorations can diffuse the output of the filter. You can try to add some rocks, caves, driftwood and live or artificial plants. They can make your aquarium more ornamental, provide some places for your fish to hide and play, as well as reduce the flow rate of your aquarium filter.

aquarium decoration

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Dense the filter media

It will be much easy for water to flow through if the filter media are sparse. When you add some media to the filter and make it denser, the water will move slowly and then you can reduce the flow.

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How to speed up the flow of your filter?

  • Add a powerhead: a powerhead will make your filter more powerful because it speeds up the water circulation, which means speeding up the flow of your filter.
  • Clean your filter: the water flow is influenced by the filter, if the filter is clogged by the waste, the flow will be weak. So you need to clean your filter regularly.
  • Reduce some filter media: more media makes it harder for water to go through, so you should reduce some filter media, but make sure the media left can clean the water efficiently.
  • Remove some decorations: decorations will diffuse the water flow, so remove some of them.


How to reduce wave maker flow?

Some people will buy a wave maker to speed up the water flow in an aquarium, sometimes the water flow will be too strong for fish to live, so how to reduce the wave maker flow? The followings are 3 simple tips:
  • Put something over the wave maker to reduce the flow, such as a sponge or filter floss. It can also serve as a mechanical filter, which can make your tank cleaner.
  • Put some driftwood to baffle the flow.
  • Let the wave maker have a rest by setting a timer. Continuous flow forced the fish to hide, if you turn it off for a while, the impact will be reduced.


What if the flow of your aquarium is too strong?

A strong flow will stress your fish. Some fish are peaceful when the environment is stable, or they will be aggressive and hurt their tank mates.

In addition, too much stress will hurt fish. Their mood, appetite and digestion will be influenced, thus causing diseases or even death.

Fish can breathe in the water, but they also need to come to the surface to breathe sometimes, or they will hurt their labyrinth organ. If the flow is too strong, they will struggle with the flow and tire themselves out when trying to swim to the surface. If they overexert, their fins might also get hurt.


The proper flow of your aquarium filter

Generally speaking, the flow rate of your filter should be 4 times your tank volume. For example, if you have a 30-gallon tank, the flow rate you need is at least 120 gph. But it is not a fixed formula, you should consider other elements, including the fish you keep, the decorations in your aquarium and so on.

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