Fish Tank Filter: Troubleshot & Fixes 2022

Filters are one of the essential pieces of any aquarium. Without them, the conditions of your tank can rapidly deteriorate.

However, on occasions, they may not work as intended, and it can lead many tank owners to wonder.

How to troubleshoot a Fish Tank Filter

There are various ways to troubleshoot water filers because they can fail or show different working levels in a couple of differing areas. You may find your filter doesn’t work at all; there is a lack of suction or the flow rate in your water is too low or too high.

Here, we will look at the function of water filters in aquariums. The issues you may face, how to resolve them, and a couple of things you ought to do for the maintenance of your filter and your tank.

Why Filters are Important in Aquariums

Every tank owner, ought to know a fish tank filter is there to maintain a healthy environment for their fish. When these filters don’t run correctly, there is a higher likelihood of an increase in toxins in the aquarium, which can lead to fish being poisoned.

Toxins stem from poor filtration, where debris and organic waste start to accumulate at the bottom of the fish tank. Once water levels deteriorate, fish stress and the chances of them falling ill increases.

As a secondary function, filters go a long way to add aeration and oxygenation into an aquarium. You may not think it, yet fish still require oxygen, and this they gather as oxygenated water passes through their gills.

aquarium filtration types

Aquarium Filtration Types

Filters will clean aquarium water in one of three ways, although you may find some filters carry out all of the functions.

Biological Filtration

Biological filtration is set up through “cycling,” and you find the best biological filters you can purchase will also need to go through this cycling period before they cannot process fish waste.

Aquarium plants will use some of this nitrogenous waste to act as a fertilizer. However, they can only do this in minimal amounts and during daylight hours as they photosynthesize. As much as they can use, it makes little effect on the downward slope toward unhealthy water without a filter. Besides, plants respire at night and will produce nitrogenous waste.

Biological filtration comprises bacteria and microorganisms, which convert fish waste into less toxic substances. If not removed, this waste rapidly becomes toxic to your fish. Biological filters convert toxic ammonia created from the waste, uneaten food, and dead plant matter into Nitrite, and then the toxic Nitrite, they convert to less harmful Nitrates. However, if you don’t remove Nitrates through your routine water changes, it can lead to kidney, liver, and eye problems for fish. Appetite suppression and lack of oxygen absorption are another couple of areas that increased Nitrates can affect fish.

The process of biological filtration happens when your water passes over a surface inside the filter where the beneficial bacteria can grow and remove these toxins or harmful elements.

Mechanical Filters

Mechanical filtration is much simpler in operation. The way this work is by filtering out any particulates or debris from the water in the same way as a filter catches tea leaves or ground coffee when making a drink.

The filter media can be a sponge, filter floss, special filter pads, or something as simple as aquarium gravel. The performance of mechanical filtration depends on a few things. The size of the filter media being the first because the more substantial the gaps, the less it can catch. The finer the media, the more it traps, but the more often it requires cleaning. You tend to find the majority of mechanical filters use multiple layers of media.

They begin with coarse and final layers being finer to deliver the best chance of cleaning everything from your water.

A few things affect mechanical filters, such as how fast water passes through them. If there are weak flow rates, debris has a chance to fall to the bottom of the tank and not be cleaned from the water. Mechanical filters won’t work if damaged, and they require frequent cleaning to be sure they operate at their optimal level.

Chemical Filtration

Chemical filtration is made by carbon or chemical compounds, which extract toxins from the water. One of the primary ones is activated carbon that can remove chemicals aggressively from the water. It does this until the carbon is fully saturated and can’t absorb any more. Thus, the reason it is essential to change carbon filters frequently.

It takes around one cubic inch of activated carbon to deliver filtration to two gallons of water for one month. To work effectively, two conditions need meeting.

Water flow: The entire volume of water needs to pass through your filter twice per hour. If water doesn’t move fast enough, it won’t face enough exposure to the carbon.

Chemical load: Hard or soft water or water you have treated and has a high level of minerals or trace elements saturates carbon at a faster rate. Plant feeding can have an impact because the carbon works so well, it will remove these before your plants can benefit from them.

Common Filter Issues, Which Require Troubleshooting

No matter which kind of filter you have, the results of them not working correctly will all lead to the same issues with your tank and your fish health.

Here are the three most common problems you can encounter with your filters.

aquarium filter issues

Issue: No Suction in My fish tank filter

The primary design of aquarium filters leads them to use a motor-operated impeller. It is their function to suck water into the housing of your fish tank filter.

It begins by drawing in water through the intake tube and pushes it through the different filter media. If at any time there is a loss of suction, then your filter will cease to work, although you can often hear the filter running. On checking, you may see there is little, or no water is drawn up the tubing.

The issue here, more often than not, is there is a blockage somewhere in the intake tubing or the impeller housing.

Fix: You need to unplug your filter and remove it from your tank. Begin to take it to pieces while visually checking for anything that may be causing the blockage. Small particles of gravel substrate can cause this problem, and you should be able to see these easily.

Rinse all the separated pieces and reassemble your clean fish tank filter impeller and motor housings. If the filter was running, yet with no suction, then it should work once assembled, and you can place it back in your fish tank.

If there is no action in the motor or the impeller after cleaning, it may be a physical problem with these. If you are unable to order spare parts or replace it under warranty, you may need to be looking at purchasing a new one.

Be aware you can’t leave it too long to do this, or your fish will suffer.

Issue: Incorrect Flow Rates

When you face this troubleshooting issue, it may not be a problem with the fish tank filter as in failure. All species of aquarium fish have their preferences for water conditions and water flow.

Fish from lakes or ponds generally like slower moving waters, while fish from mountain streams, rivers, and other swift-flowing bodies of water like stronger currents. Tank owners need to know the differences between these preferences before stocking tanks. A filter may be delivering a gentle current, yet your fish like a faster flow, and vice versa.

Fix: Because of this, some filters now come with flow rate adjusters, so you can adjust the filter intake, which results in a slower or faster output into your tank. If you find you are on the fastest setting and it is still too low, then you may be looking to upgrade to a larger, more powerful filter or adding a secondary source of filtration.

If your flow rate is too high, you can add sponge in line with your fish tank filter to reduce flow, or it may be you need to obtain a smaller, less powerful filter.

Issue: Filter Not Running

There can be instances where you get up in the morning or return home from work, and there is silence around your fish tank.

Fix: Disconnect your filter, and check if there is a blockage as in step one. If that isn’t the problem, it could be something else. Power surges or power outages can affect filters on some occasions. You can leave it disconnected for a while, as the fish tank filter may need a while to readjust itself before it will reset and begin running again. While doing this, you can trace along the power cords to check for blown fuses or a tripped breaker.

If your filter doesn’t work after an hour, it may have died on you, and you will be looking at a repair or a replacement. The biggest issue will be you have no way of knowing how long it wasn’t working, and your fish could be starting to suffer. Air pumps are ideal in this scenario so that you can keep oxygenating the water.

Maintaining Optimum Filter Operation

aquarium Optimum Filter Operation

You can find a couple of things that may have an impact on fish tank filter performance, even when there is no problem. Here are a few things some tank owners often overlook.

  • Filter Pump Chamber: Be sure you have water in this chamber. If it is full of air, then that is all it can suck instead of water.
  • Aquarium Water Levels: Check the manufacturer’s instructions on how high your water level needs to be for your filter to operate correctly. Many filters need the water level to be around an inch from the lip of the fish tank filter.
  • Air pumps and stones: If you have air stones in your tank, make sure the rising bubbles are not around your filter. This can stop the correct functioning as your filter begins to draw in air as well as water.


Most fish tank filter issues are quickly resolved as they stem from blockages, or the filters are the wrong size. If you find your filter broken, then you need a quick fix, or the chance to get a replacement.

Keeping a spare water filter may appear to be overkill, yet aside from a blockage in your filter, you most often find they die and stop working rather than not working correctly.