How Often to Change Aquarium Filter (For All Media Types)

Last Updated: September 17, 2023 by Flora Gibbins

When it comes to the question “How often to change your aquarium filter”, you are better off evaluating each type of media in the filter and taking care of them as needed.

Actually…

This approach works better because you can easily manage the aquarium filter’s role in sustaining the biofilter.

Overview

In reality, an aquarium filter is a combination of filters working together to achieve a common goal. You will have a much healthier ecosystem in the fish tank when you treat each filter media as a separate filter.

Depending on the media type, age of the aquarium, and bioload, it may take years before you change a specific media. On the other side of the spectrum, you may need to change some media every few weeks.

5 Filter Media Types and When to Change Them

Activated Carbon

Activated Carbon is used for chemical filtration. It traps gases and numerous dissolved molecules that make the water smell bad or discolor it.

Regardless of the age of the tank, you will most likely need to change activated carbon monthly. The exception to this is tannin-rich “black tanks” and heavily planted tanks.

Floss or Filter Pad

Technically filter floss or filter pads are classified as a type of mechanical filter. It removes small particles of food and other debris that might be floating in the aquarium water.

Floss is also where good bacteria are most likely to colonize.

Don’t replace all of the floss unless it is starting to rot. What I do is replace about 10% every year so that I don’t have all the floss showing signs of rot at once.

In all my years of aquarium keeping, I’ve had floss in perfectly good condition after 6+ years. Still, I like to be prepared.

You can use water removed from the tank during a routine water change as long as it is in good condition.

Zeolites

Ammonia surges are most likely to happen in tanks less than a year old and one year after medicating the tank. Both of these situations lead to massive disruption of the biofilter.

During these times, I recommend using Zeolites and changing them every 2 – 4 weeks. You will also need to monitor ammonia levels in the tank water daily.

If you don’t see signs of ammonia just before changing the zeolites, you can cut the amount back. Since Zeolites do absorb ammonia, they can interfere with the development of nitrifying bacteria.

Ceramic Filter Rings

Ceramic filter rings are classified as biological filter media. These rings are meant to house good bacteria that break down toxic waste in the tank. The rings themselves don’t degrade, so they will last for the lifetime of the tank and then some.

Water Softeners

Even with partial water changes, the general hardness of the tank water will go up steadily. Eventually, this can have a harmful impact on the pH, as well as the fish in the tank.

I usually don’t use water softeners such as peat moss or softening pillows during the first few years unless the fish need soft water.

Scheduling for changing a water softening component depends on the product. Some have to be recharged in salt water every 48 hours. Others can stay in the tank for weeks to months.

Managing Sponge Filters

For the most part, you will be using a canister filter or HOB filter. Over time, you may develop an interest in fish that require gentler water currents.

Here’s a short video to learn about a HOB filter: 

A sponge filter is useful when you don’t want to rely on diffusers or reduced inlets that may impair filter function.

Cleaning sponge filters is very different because you only have one kind of media to deal with.

Typically, you will need to rinse the sponge-based filter cartridge every 3 – 6 weeks or it will clog up and stop working right. 

Never use running tap water. Instead, rinse the sponge in a bucket of clean water or aged aquarium water.

Frequent rinses have a bad impact on the biological filter housed within the sponge.

Double sponge filters can help reduce this impact as long as you stagger rinsing so that you only clean one sponge at a time.

Your other choice is to use multiple sponge units in the tank. The more units you have, the fewer times you will need to rinse each sponge.

Undergravel Filters

If there is one kind of filter I wish didn’t exist, it’s the undergravel filter. Over the years, many people have “given them a try”, only to regret it when it came time to clean the filter.

Other than the air stones in the risers, there aren’t any media to change in an undergravel filter. Instead, the filter pulls debris through the gravel into an empty space below it.

Unfortunately, even if you can get a siphon into the riser, you won’t be able to simply pull out all the debris trapped under the plate.

If you fail to pull the debris out, eventually, it will build up into a sludge that will prevent further water flow through the gravel.

Before that happens, the fish tank may develop nitrite surges, ammonia surges, and increasingly cloudy or foul-smelling tank water.

There is no real answer to the question “how often to change an aquarium filter?” when it comes to undergravel filters. Since you can’t readily maintain them, it’s only a matter of time before the ecosystem in the tank fails.

Whether you aim for routine maintenance or managing ecosystem failure, your questions are more likely to be:

• Where am I going to put my fish while I pull up all the gravel and disrupt the entire tank to get at the debris?
• How long will it take another filter to clean up all the gunk that gets released into the water?
• How many filter socks filled with activated carbon or other media will I need to put in the tank?

Fun Fact #2: We strongly suggest that you gain knowledge on how to raise pH in aquarium to ensure your pet fish’s safety!

If you use filter socks, here’s a guide on how to clean them.

Frequently Asked Questions

1. How Much Damage Do Complete Filter Changes Cause To Biological Filtration?

This depends on how you address where good bacteria are most likely to colonize. For example, if the filter comes with a plastic screen that doesn’t need washing, there will be less damage to the biofilter.

By the same token, if you don’t replace all the floss or put ceramic rings in hot water, a good bit of the biofilter should survive.

Your best option is still staggering media replacement so that you don’t change all of it at one time. Other than that, the fewer changes you make to the media, the better.

Unless the floss or ceramic rings are clogged with gunk and are not letting any water through, it is best to leave them alone.

2. Why Does My Aquarium Get Cloudy After Changing The Filter?

This depends largely on what happens while you are changing the filter, and which media you are changing.

Usually, you will see some black cloudiness after changing the activated carbon no matter how much you rinse it. This should disappear in a few hours.

In a similar fashion, dust from zeolites will produce a white haze.

Rinsing the floss can also result in green, brown, or yellow haze depending on how much gunk is released from the floss. This should also clear up in a few hours.

To speed up the removal of excess debris, you can put a second filter in the tank with just floss. I use a bubble-up filter for this with an independent pump. Once the water is clear, I remove the secondary filter and let the floss dry out so I can use it next time it is needed.

3. Does The Filter Type Alter When I Should Change The Media In It?

The filter size matters more than the type. In general, the more filter media you have, the less often it will need to be rinsed or changed.

Bioload also has an impact on how often you change the media. Even if you have a filter rated for the tank size, it may still need cleaning more often if the fish produce more waste than the filter can handle.

Conclusion

The answer to the question “how often to change an aquarium filter?” depends on many factors. Along with the actual media used in the filter, you also need to consider the bioload and other elements in the tank that offset it. 

Plants, debris scavengers, fish size, and fish type all have an impact on how long filter media lasts and how well it works.