How to Change an Aquarium Filter Cartridge without Losing Bacteria?

Being an aquarist means you already understand the importance of bacteria inside the aquarium.

It helps in breaking down the toxic ammonia in nitrites and nitrates, making the water safe for all the inhabitants.

The majority of the beneficial bacteria gradually start accumulating on the aquarium filter.

However, when the time comes to change the aquarium filter cartridge, most—if not all—of the bacteria end up getting removed.

This change in the number of bacteria can have a major impact on the overall health of the inhabitants of your aquarium.

The new filter usually takes a few weeks to build up bacteria, but even a few days of the reduced amount of bacteria can do the damage.

Fortunately, there are ways you can change the aquarium filter cartridge without losing beneficial bacteria.

Three Ways of Changing Aquarium Filter Cartridge without Bacteria Loss

There are three main ways of preventing bacteria loss when changing the aquarium filter cartridge.

These methods are rather simple and require keeping the old cartridge of the filter.

Therefore, whether you are changing the entire filter or just the cartridge, make sure to keep the old cartridge to support the new one.

This helps the new media to accumulate the bacteria from the old one and save the potential disaster that might occur in the tank otherwise. Here are three methods:

Leaving the Old Filter in the Tank

Keeping the old filter or cartridge in the tank along with the new one for four to six weeks is the most effective and easiest method to prevent bacteria loss.

You just need to install the new one and remove the old one after a month or so.

This method will give the new filter cartridge sufficient time to build up the beneficial bacteria from the old medium to maintain the balance in the aquarium.

However, it is essential that you keep a close watch on the flow rates. The high rate of flow is bound to disturb the fishes, particularly the young and small ones.

A rapid flow rate increases the stress levels of the fishes as they have constantly keep swimming against the current.

A slow flow rate is important for not just the fishes but also the live plants, as it assists in maintaining a healthy level of carbon dioxide.

Filter pads can be used to reduce the flow rate if there is a need. If you want, you can even leave the old cartridge in the aquarium permanently unless it has broken down.

Reusing the Media of the Old Filter

This option is ideal if you are removing the entire filter. All you have to do is remove the media from the old filter and place it in the new filter.

The majority of the beneficial bacteria are stored in the media itself. This method will save the majority of the bacteria.

The main problem with this method is that both the new and old filters must have the same shape and size as the cartridge.

If you have purchased a new filter from a different brand or have upgraded to a bigger one then it might not be possible to fit the cartridge from the old filter into the new one.

Moreover, you must make sure that the old cartridge is in good condition before you put it in the new filter. A broken one or the cartridge which is falling apart shouldn’t be reused.

Keep the old cartridge in the new filter for four to six weeks before changing it to a new one.

By this time sufficient bacteria would have accumulated on the new filter itself, making it safe to switch to the new media without causing any drastic bacteria loss.

Colonizing the New Filter

In case you can’t or don’t want to keep two filters running simultaneously and if the old cartridge is not fitting in the new filter, there is still another option left.

When taking out the old filter, take out its cartridge. Check to see if it is in good condition and simply place it inside the aquarium with the new filter.

As long as the media is not falling apart, it will work in the same way as fitting the old cartridge into the new filter.

Within a month, the new filter would have become colonized with bacteria from the old cartridge.

While it is safe to run two filters simultaneously in the aquarium permanently or keep reusing the old cartridge inside the new filter until it starts breaking, this method should only be used for a month.

Once the month is up, immediately remove the old cartridge from the aquarium as it can start causing problems.

These three are the most effective means of changing the aquarium filter cartridge without losing bacteria.

Keep monitoring the tank to ensure everything is stable after these changes are made.

Understanding Biological Filtration and Importance of Bacteria Loss Prevention

The majority of the new aquarists are unaware of the important role played by bacteria in an aquarium.

Many are so quick and eager to upgrade the filter of their tank that they remove the majority of the beneficial bacteria without realizing the impact it could cause.

This usually leads to grave consequences.

It is essential for all aquarium owners to realize why it is important to prevent bacteria loss when changing filters or even when only changing the cartridge of the filter.

Biological filtration is the method that helps in purifying the water in the aquarium using microbes which keep the aquarium healthy.

The beneficial bacteria which gradually builds up on the filter and the cartridge is responsible for operating the main system of waste disposal in the tank.

All the waste from uneaten food and your fishes release ammonia in the aquarium water. A high amount of this ammonia can deteriorate the health of the fishes and may even from fatal.

Ammonia is broken down by beneficial bacteria.

As mentioned above, ammonia breaks down in nitrites and then into nitrates and reduces toxicity.

The nitrates are then eliminated from the water during the usual water change. This is the biological filtration process that maintains the balance in the aquarium and keeps it healthy.

Does The Aquarium Filter Cartridge Really Need Changing?

This is an important question to ponder upon that the experienced aquarists consider but not many new ones do.

Often there isn’t even a need to change the cartridge in the aquarium.

However, cleaning and maintaining the tank is essential, many opt to change the cartridge during the regular cleaning schedule for a safe time.

This is not a wise move since it will merely remove beneficial bacteria unnecessarily and you will be wasting more money due to frequent cartridge changes.

Just like there is no need to change the filter unless it is malfunctioning or broken, you don’t have to change the filter cartridge until it is torn or falling apart.

Therefore, before you decide to change the aquarium filter cartridge, determine whether it really needs to be changed.

If it is in good shape, the cartridge can probably do its job effectively for the next few months.

There is no need to risk beneficial bacteria loss and stress out your fishes unless there really is a need to add in a new filter cartridge.

Common Misconceptions about Aquarium Filters

There are various misunderstandings regarding the aquarium and its filters that the majority of the aquarists end up believing due to lack of research.

There are two rather common misconceptions about biological filters which often lead to disasters for new aquarium owners.

These misconceptions are:

  • Bacteria which consumes the ammonia and nitrite only lives inside the filter, which means the bacteria that builds up outside the filter can be removed
  • Majority of the beneficial bacteria is in the media, like filter sponge and bio rings

This also makes new aquarists believe that switching the filter will always result in a biological crash and affect the health of the fishes.

As a result, they avoid changing the filters and the cartridge in hopes of keeping the beneficial bacteria.

This is not completely true. Good bacteria are actually all over the aquarium, provided the filter is efficiently working and the aquarium is healthy.

While the majority of bacteria build up in and on the filter, they can also be found on the aquarium glass, plants, ornaments, and gravel.

This misconception makes them believe that any bacteria present in the aquarium, aside from the filter, is bad bacteria and must be removed.

Many new aquarium owners end up cleaning up the bacteria and, as a result, witness a decline in the health of their fishes, and even a few fatalities.

It is true that removing the filter means you lose the majority of the bacteria, which can cause a biological crash.

However, in some cases, if there is a sufficient amount of bacteria in other parts of the aquarium, changing the filter won’t result in a crash.

While it might be safe to change the aquarium filter cartridge or remove the entire filter without using the old one to prevent bacteria loss, it is best to be safe than sorry.

Therefore, it is recommended to use one of the three mentioned methods to prevent bacteria loss when making the change.

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