Best Biological Filter Media: Your Fish Will Thank You!

Almost all aquarium filters now come with at least three filtrations, including mechanical, chemical, and biological ones.

And the last one is exceptionally useful to create a stable and natural environment with beneficial bacteria for your fish. To be more specific, there is a filter media where those bacteria settle on and create colonies.

Useful as it is, however, the media should be replaced every three or six months at a minimum, depending on the water environment.

For that reason, you search for the best biological filter media and reach our post. Fortunately, you do not have to search any further. Here we discuss all you need to know about biological filter media.

Let’s start!

See more:

Best Quietest Aquarium Filters

Top 5 Best Biological Filter Media Reviews

Product Images Product Name Editor's Rating Prices
Seachem Matrix Bio Media 1 Liter 4.5 out of 5 stars (4.5 / 5) See price on Amazon
EHEIM Substrat Pro Biological Filter Media 4.8 out of 5 stars (4.8 / 5) See price on Amazon
Fluval Biomax Filter Media 4.8 out of 5 stars (4.8 / 5) See price on Amazon
Marineland Bio-Filter Balls 4.7 out of 5 stars (4.7 / 5) See price on Amazon
CerMedia MarinePure Sphere Bio-Filter Media 4.7 out of 5 stars (4.7 / 5) See price on Amazon

Seachem Matrix Bio Media 1 Liter

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The Seachem Matrix Bio Media 1 Liter is as known as one of the best biological filter media for aquarium, for good reason.

Made of the naturally mined and inert pumice stones, the media features a ceramic-like and large-pore look. Thus, the Seachem Matrix Bio Media offers rough and internally macroporous surfaces, ideal for bacteria to live and colonize in. As a result, you can expect more bio-load inside your tank.

Even better, the media is proved to work out of the box with all waters.


  • Usable in loose or in a filter bag
  • Lightweight, yet never float-away
  • Highly porous surface
  • Free from replacement


  • Not work with a drip tray system

EHEIM Substrat Pro Biological Filter Media

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Excitingly enough, there are almost no complaints about the EHEIM Substrat Pro Biological Filter Media. The product’s quality sells itself as the best biological filter media for reef tank

This sintered-glass media comes in a spherical shape, giving a better density for the intensive colonization of beneficial bacteria. Such a high volume of bacteria will result in fewer nitrate loads and a more healthy aquatic environment.

We also like that this media is versatile for both fresh and saltwater and reusable after being carefully risen.


  • Optimized sintered-glass biological filter media
  • High-density spherical shape for dense colonization
  • Versatile for fresh and salt-water environments
  • Reusable after cleaning and no frequent exchange required


  • A bit pricey

Fluval Biomax Filter Media

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Bacteria like the porous system to colonize in. Thus, the bio-ring media such as the Fluval BioMax Bio Rings is definitely more helpful than the smooth biological filter media. Especially, many consumers praise this as the best biological filter media for freshwater aquarium.

Moreover, the ring design allows the water to flow through more quickly which even fastens the colonization process for deep cleaning.

The silica and aluminum oxide – the main materials of the media makes it usable for all aquarium from freshwater, marine water, to reef tanks.


  • Very cheap
  • Available to use in a filter bag or a canister filter
  • Versatile for various aquatic areas


  • Required to replace every six months

Marineland Bio-Filter Balls

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If you only have one or two fish and the tank environment is not very large, then some Marineland Biological Filtration Bio-Filter Balls are an ideal choice under budget. Within a pack, there are up to 90 balls having a multi-faceted surface for the bacteria.

In addition, these balls are reusable once you clean out off buildup under the water flow.

Just a small note is, the balls are just as small as the pinky nail. This size is sometimes ineffective and even not able to fit a small canister filter.


  • Among the cheapest media in the market
  • Multi-faceted balls for more bacteria
  • Easy to clean and maintain


  • Too small for some filters

CerMedia MarinePure Sphere Bio-Filter Media

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CerMedia MarinePure Sphere Bio-Filter Media is the best biological filter media saltwater ever thanks to the Thin Bio-Film technology.

This technology supports the vast surface and interconnected pores at the same time so that effective bacteria can colonize and flourish valuable nutrients. Moreover, the water flows through the sphere balls to utilize the surface and flush the dead biofilm away easily.


  • Vast surface and interconnected pores for high bioload
  • Less maintenance and cleaning
  • Thin Bio-Film technology available


  • Very costly

Why Do I Need a Biological Filter?

How does a biological filtration help with?

It is a common mistake for the beginners who raise their first fish that the purer water environment is, the stronger the fish will live.

Nonetheless, the real aquatic habitat contains hundreds of microorganisms that naturally filter out debris and recycle nutrients for animals and plants living in the environment.

Take the Nitrosomonas and Nitrobacter, for instance.

The Nitrosomonas is a species of aquatic bacteria that consume Ammonia (NH3) – the toxic byproduct of the fish or the waste product from uneaten foods, and convert it into Nitrite (NO2).

Afterward, the Nitrobacter consumes and converts Nitrite into Nitrate (NO3), which are harmless or even useful to aquatic life such as algae and plants. Those plants are, hilariously, foods or accommodations for the fish in the tank.

These two bacteria are naturally included in the water. However, they can not multiply as fast as possible to handle all the Ammonia and Nitrite produced. As a result, your fish might be suffering from toxics or even dead.

In such a situation, the biological filter is in place to stimulate the nitrogen cycle, using two additional bacteria: the denitrifying bacteria and nitrifying bacteria.

How Often Do I Need to Change My BFM?

It depends on many factors: the water source, the tank capacity, the number of fish, the quality of the filter and the biological filter media (BFM) themselves, and so on.

However, you should replace the BFM every three to six months.

First off, you had better refer to the recommendations of the media lifespan, which is usually mentioned clearly in the manual guide.

Secondly, when the media is too clogged with bio-load and waste levels and your fish might be ill, then it is time to do a deep clean. The video above will help. 

Yet, if the cleaning is still not enough, then you need to replace the media ahead of the recommended time.

Be careful not to lose beneficial bacteria, using one among the following methods:

  • Run the two filters at the same time. Do not throw the old filter away. Instead, let it be with the new biological filter for one month so that the new one can cultivate and re-colonize the remaining bacteria. Also, take care of the water flow rate suitable for the new media.
  • Use the new filter with the old media. However, make sure that your old media is still in good shape and that the two parts perfectly fit with each other.
  • Simply put the new filter next to the old media. Of course, throw the old filter away. After a while, the bacteria will colonize from the old media to the new filter.

With Lots of BFM, Do I Still Need the Mechanical and Chemical Ones?

Yes, still!

First off, the mechanical, chemical and biological filtrations are helpful in different ways.

    • Mechanical filtration: The mechanical media merely handles solids passing through. Thus, it has nothing to do with chemicals.


  • Chemical filtration: With activated carbon and resins, the chemical media helps get rid of dissolved particles from the water.
  • Biological filtration: Stimulate the nitrogen process to procedure harmless nitrate.


Secondly, these three filtrations are vital to the efficiency and lifespan of one another.

For example, the mechanical media removes unsightly particles to prevent build-ups and toxic byproducts (NH3 and NO2). As a result, biological media can work less and last longer.

In addition, the chemical filter media is also contributive to the biological media. It reduces the number of harmful substances first before reach the biological media.

FAQs about Best Biological Filtration Media

#1. Why are ammonia, nitrite, and nitrate toxics?

Because they are byproducts of fish, which will build up and damage the water quality. Consequently, aquatic life can reduce the growth rate, suffer from poor appetite, sluggish performance, or even death.

#2. What makes good filter media?

Good media, first of all, should be compatible with your current filter (e.g. mechanical filter, chemical filter, biofilter, etc.) and the aquatic environment. For example, the best biological filter media for planted tank might not be the best biological canister filter media.

Secondly, take the materials, texture, and characteristics of the media in mind. Normally, you might choose between sand or glass pearl media. The earlier is simple to maintain and capture the dirt very well. However, the sand clumps and calcifies after a time. The glass pearl media, meanwhile, is excellent at deep filtration and requires less maintenance. Nonetheless, it is expensive.

Thirdly, the media should be easy to install and maintain.

#3. What types of biofilter media to use?

The types of biological filter media often vary by materials. Sand or glass pearl media are the two examples. Otherwise, you can also go for ceramics, natural minerals, or plastic ones.

The media is different by shapes and sizes, as well – for example, blocks, rings, spheres, and so on.

#4. How much biofilter media do I need?

There is no fixed formula to calculate the number of media properly. It depends on the size of the tank, the amount of food, the number of fish, water parameters and most importantly, the characteristics of the media itself.

Fortunately, the manufacturers of the biofilter media often suggest a specific number of media per gallon. Then, you can try and adjust the amount of media.

#5. How to maintain the biofilter media?

Most of the time, lukewarm water is enough to clean off the solids and blockages. With media materials that are fragile, you should remove it in parts and replace them with new material.

Wrapping Up

We hope that you already find out the best biological filter media for your fish tank and wish that your lovely fish will also live strong and healthy.

If you still not find the best choice, take one more deep look at all biofilter media above again and make a wise choice.


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