Fish Tank Filter Running Slow- Fix it in A Few Minutes

Found your fish tank filter running slower than before? Whoo! You are in the same shoes as me. I also found my fish tank filter running slow yesterday. 

But I am not worried as I know why it is happening and how to sort it out. Due to the huge pressure of working, I couldn’t clean the filter for some days, and meanwhile, debris accumulated in my filter.

If you are having the same problem, it may occur due to dirt gathering in the hose pipe, filter media or impeller, impeller break, or usage of more water.

But whatever the problem is, if you follow the instructions properly that I am going to mention below, hopefully, your problem will be solved. 

Why is the Fish Tank Filter Running Slow- 5 Causes With Their Solutions 

1.More Usage of Water

First of all, make it clear that you have adjusted a perfect filter for your aquarium that is balanced with the water quantity. 

You know that every filter has a definite capacity for filtering water. If you are not conscious of that and take a small filter for a huge tank, it has to clean a lot of water at a time that is beyond its ability. 

At that point, the filter won’t continue smoothly and after some days it will start running slowly. The filter hose and impeller problem can also be initiated.


To solve this problem, before adjusting a filter, you should choose one that is adjustable with your filter size and then adjust it properly. 

2. Debris Accumulation 

Simply think of a matter! If you have a lot of debris gathered in your path, can you walk smoothly there? No, right? 

In the same way, whenever a huge amount of debris accumulates in your filter, it won’t work properly. To get an idea of this matter, firstly, you have to understand why such a problem occurs.

Look, debris can be clogged in the filter in many ways. If you don’t maintain a regular cleaning schedule, the dirt and the excess materials will be gathered in the filter.

As a result, the debris will create a thick layer which will decrease the activities of the aquarium filter and thus the filter will run slow. 


If you are going through the same problem, let me suggest my solution. Keep in mind that you can’t always clean 100% of the filter. So you have to reduce the maximum amount of dirt.

Firstly, power off the aquarium and then take out the filter after unplugging it. Then, clean the dirt carefully so that no parts are destroyed. 

In the case of cleaning, I always maintain the issue of bacteria. As germs and bacteria arise from those, I remain fully concerned about eradicating them. 

Hence, you should also confirm that at least the bacterial growth is resisted by your cleaning. Thus, you can get rid of the dirt problem.

3. Hose Issues

Next, let’s talk about the hose issues. Confused? Let me make it clear with my example. The same problem of dirt can also irritate you in the hose pipe section. 

As water passes from the aquarium to the filter by the hose pipe, mineral matter and other kinds of dirty things can also accumulate there. 

In this case, the flow rate can be slow though you have a clean filter. But it completely depends on your concern. 

Don’t make mistakes like me as I didn’t understand that my hoses were dirty and that is ruining the flow speed. If you find your filter clean, immediately look at the hoses carefully. 


The same solution that I suggested to you is also applicable here. Only the difference lies in the technique. After unplugging the filter, take out the hoses.

Then, soak the hoses in a tub of warm water for 30 minutes. The warm water will help to remove the debris mostly. Then, take a brush and clean the hose properly. Soon, the flow rate will be increased.

4. Improper Flow Rate

Maintenance of a filter is not as easy as many people think. While adjusting the flow rate of the filter, you will understand the facts properly.

Some filters come with the feature of adjusting the flow rate. If you have that type of filter and you don’t adjust it properly, the filter will not pass enough water.

As a result, the water flow will be delayed and sometimes it may introduce malfunctioning of the filter and may stop.


Trust me, it won’t be a big issue if you follow the instructions properly labeled in the filter. You may also take the help of YouTube videos or an expert one in the case of adjusting it. 

5. Broken Impeller

Last but not the least! Here I will describe the impeller problems. Look, two types of problems can appear here. Impeller blockage and impeller break.

Impeller blockage occurs due to the accumulation of dirt that I have already described in the hose or filter problem. You can easily get an idea about the facts from the above suggestions.

On the other hand, the impeller can also be broken. It can happen due to various reasons. For instance, excessive flow rate or wrong adjustments.


As I have said, you can get an idea about the cleaning from the upper portion. But, if it is broken, you have to disconnect the filter and take out the impeller. Then, replace the impeller with a new one. 

How to Increase the Flow of a Filter? 

If you find that your filter is running slow, you can try some steps mentioned below. I always try to maintain these points to keep my flow rate perfect.

Clean the Filter Media

As I have described to you, over time, filter media can become clogged with debris or dirt. Hence, try to keep the media clean by regular cleanliness activities. You can also replace it in serious moments.

Check for Blockages

Always inspect the filter and tubes if there are any blockages or obstructions. Sometimes, debris can accumulate and impede water flow. In a regular checking schedule, you can get rid of it.

Adjust the Flow Control

Many aquarium filters have a flow control knob for emergency moments. If your filter has such a knob, adjust it to increase the flow rate.

Use a Larger Pump

Whenever you find that your filter allows for a larger pump, consider upgrading to a more powerful pump. But, before that, you have to make sure that the new pump is compatible with your filter system.

Check for Air Bubbles

Sometimes air bubbles can reduce the water flow. To cope with the system, make sure there are no air leaks in the filter system, and if needed, bleed excess air from the system.

Remove Excess Waste

Regularly remove uneaten food, debris, and waste from the aquarium as excessive organic matter can contribute to clogs and reduced flow.

When I Need Do You Need to Change the Filter? 

You should replace the filter after you have tried all the techniques, but still, the filter is not serving better. For the aquatic inhabitants and fish species, clean water is a mandatory issue.

At least, those who have enough knowledge about their aquarium, consider that filter is obligatory for a clean environment for the fish.

Hence, you should first try the methods that I explained before. If you find that no technique is enough to increase the flow rate, be sure that your filter needs to be replaced.

In that case, consider your tank size and water quality so that the new filter can be perfectly adjusted or compatible with the aquarium ecology. 


Can a low water level affect the filter activities?

Yeah! If the water level is too low, it can impact filter efficiency negatively. That’s why ensure the water level is within the recommended range for your filter.

Could a power outage affect filter performance?

Certainly, it can disrupt biological filtration badly as the filter system gets stopped without electricity. Consider adding a battery-powered air pump for aeration during outages.

How can I prevent filter issues in the future?

You just need to inspect and clean the filter regularly, monitor water parameters, and follow the instructions for maintenance.

Final Words

Well, I tried to focus on the main points that may create troubling situations for you. I want to mention that the solutions that I provided here are completely based on my experience. 

In some cases, these may vary a little, but the basic cleaning or sorting technique will be the same. If you need a more clear answer, you can check other articles on my website.

Or, you may visit an aquarium expert for your solution. But make sure that the filter is not neglected. Otherwise, it will destroy your aquarium ecology.

Howard Parker

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