Best Biological Filter Media? – 2023 Picks

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If you have found this page then you probably already understand the importance of media for your aquarium. But, not just any old media will do. You want to find the best biological filter media to ensure your tank has the cleanest water possible. 

As a long time aquarium owner and fish keeper I can certainly relate. In this article I will dive deep into the details of bio filtration and media, as well as my  personal recommendations for best bio media.

In this article I review the following biological filter media:

Importance of bio filter media

Did you know that bio filter media doesn’t actually filter out ammonia and nitrite? It’s true. Bio media actually serves as a home for beneficial bacteria to live. It is these bacteria that are responsible for consuming and converting this ammonia into the less harmful nitrate.

While these bacteria will take up residence nearly everywhere in your aquarium we need to optimize their function. This is done by giving them a home where millions and even billions of bacteria cells can flourish. Not only are they provided with a great home, we put them in a filter where they receive lots of water flow. This provides them ready access to their favorite foods ammonia, nitrite, and even nitrate. 

These biological filter media are made of very porous materials like ceramic, pumice, glass, and other substances. 

As with anything you put in your aquarium rinse thoroughly first. Biological filter media can be very dusty when new. 

The Best bio filter media

As you have just read, it’s important to give our little bacterial friends the best home we can. So let’s take a look at my top picks for the best bio filter media on the market.

Biohome Ultimate Filter Media

Biohome Ultimate Filter Media is considered a premium media in the aquarium world. It is made from sintered glass which is a combination of silica sand and recycled glass that is then oven fired. This process creates a pellet that is extremely porous with minute spaces for bacteria to thrive.

This media is available in 1, 2 and 5 pound bags. It also has a fairly good lifespan lasting 1-5 years and in some cases longer.

All media will support aerobic bacteria but not all support the anaerobic kind. Biohome claims that its media will support both. Anaerobic bacteria are desired because they are the only bacteria that will reduce nitrate levels. Without these bacteria the only way to control nitrate levels is through frequent water changes. 

The Ultimate Filter Media goes a step further beyond biohomes other media in that it contains iron and manganese to support bacterial growth. 


  • Supports nitrifying & denitrifying bacteria
  • Large even for a canister filter
  • Pellets are small enough to fit in most filters
  • Made of natural recycled materials


  • More Expensive than other options
  • May initially discolor water

Seachem Matrix Bio Media

Seachem is a well known company in the aquarium space and for good reason. Seachem Matrix Bio Media isn’t just any cheap pumice stone as its detractors may claim. It is a specific type of pumice that is carefully selected for high porosity, pore size, durability, and inert nature. 

Grain size varies but each piece is about 10 mm (0.4 inches) in diameter. This media provides both an external and internal surface area for bacteria to grow. This means that it is capable of supporting nitrifying and denitrifying bacteria. You will, however, need a large amount of media to reap the benefit of the denitrifying bacteria. 

While this is a great bio media to use in your fish tank there seems to be a common issue. Many people report other types of stones in their media besides pumice. These are darker colored stones such as obsidian. Sometimes it’s just a few, other times quite a bit more. 

Seachem states that this material is a natural product that is mined. This means that there are other naturally occurring stones that get mixed in. Most of this non-pumice material is removed by hand but some gets missed. So don’t be alarmed if you find a few dark rocks in the jar. 

Aside from this annoying occurrence I still think this is a great product. It also has a very long life and should theoretically last forever with regular rinses. 


  • Carefully researched and selected pumice
  • Capable of supporting nitrifying and denitrifying bacteria
  • Small enough to fit in most filters
  • Extremely long life


  • Sometimes adulterated with non-pumice stones

Fluval Biomax Bio Rings

Fluval Biomax Bio Rings are a very popular option when selecting a media. They are also included with most of Fluvals top rated canister filters

These bio rings are a manufactured inert ceramic cylinder with a hollow center. These cylinders are not tumbled or polished during the manufacturing process. This creates a rough, complex, porous design with lots of surface area for bacteria. 

Since these bio rings are designed for canister filters they are larger in size than some other media. So if you are looking for something to put into your “hang on back” style filter you should find something else. They likely won’t fit into your small filter housing. 

My biggest complaint with this product is the stated 6 month replacement period. This is much shorter than most other comparable media. Being an inert ceramic product the biomax bio rings should last longer than this. This however, is likely just marketing to sell more product. Unless the rings become clogged with gunk that cannot be rinsed off they can be kept. 


  • Trusted & established brand
  • Very porous hollow cylinder design
  • Relatively inexpensive
  • Ceramic


  • Short 6 month life
  • Too large for small filters

Marineland Bio-Filter Balls

Marineland bio-filter balls are black plastic balls with a complex inner pattern. They are designed this way to create maximum surface area for bacteria. While this is true, they don’t technically have as much surface area as a ceramic, pumice, or sintered glass media. 

They do however have a very long life. In fact, the only time they need to be replaced is if they break. I know of one person who as been using the same bio balls for 12 years! They are also easier to clean than a more finely porous media. 

These bio balls are fairly small in size. They measure about 19.5 mm or the size of a quarter. So if you have a large filter you will likely have to buy multiple boxes. On the flip side, these will fit into smaller filters unlike some larger bio balls. 


  • Not dusty like other medias
  • Very long life
  • Easy to clean
  • Affordable


  • Not as porous as other medias

EHEIM Substrat Pro Biological Filter Media

Sintered glass media are considered some of the best types of bio media due to their high porosity. This is especially true of Eheim Substrat Pro biological filter media. These little (¼” or 6-10mm) pearl shaped sintered glass beads have a surface area of 1800 sq ft per gallon of media. This will support an army of denitrifying bacteria to keep your water clean.

Eheim claims this media should be replaced every 3-6 months. This claim is likely just made to sell more media. With a little care you should be able to gently rinse and reuse this media many times over. 

Being a premium, high performance media, Substrat Pro is expensive compared to some other options. This is especially true if you follow their recommended 3-6 month replacement interval. But Eheim is a long trusted company that makes quality products so you get what you pay for in the end. 


  • Very porous structure supports tons of bacteria
  • Made from sintered glass
  • Eheim is well known for quality
  • Small enough for most filters


  • More expensive than other options

Which is The Best Biological Filter Media?

All 5 of these media have served many thousands of aquariums well. But which is the best? This is a tough choice for me but I’d have to say the Seachem Matrix Bio Media. Despite my annoyance at the occasional non-pumice stones that make it into the container it’s still my top choice.

Why? Because it is made from carefully selected natural pumice that provides a home for nitrifying and denitrifying bacteria. This not only helps keep your water cleaner but reduces the amount of water changes needed to reduce nitrate. It’s also a totally natural product unlike some of the others I have mentioned. 

Why Is Bacteria So Important?

Fish create waste products as they digest the food that is given to them. The primary waste product, and the one we are most concerned about, is ammonia. Ammonia is very harmful to fish and other aquatic pets in any amount. That’s why it is important that it be removed as quickly as possible from the fish tank water.

Nitrogen cycle diagram

Fortunately, nature has provided us a way to do just this. It’s called the nitrogen cycle. The aquarium nitrogen cycle is the term used to describe the process by which ammonia is transformed into nitrate. Nitrate is much more benign than ammonia and is only harmful at high levels. This is what we remove when we do our water changes. 

But, some media are even capable of supporting anaerobic bacteria which will feed on the nitrate. As the name implies, anaerobic bacteria live in environments devoid of oxygen. For these bacteria to survive and thrive we need a very micro porous bio media. These media have such a structure that oxygen is not able to penetrate to the interior of the pellet or stone. This provides the much needed habitat for these special bacteria. 

Why Is Bio Filter Media Needed?

Have you ever noticed that slippery, slimy film on everything when you clean your fish tank? That’s biofilm, or more specifically bacteria. These are our friends that clean the water of ammonia, and nitrite. 

The problem is that when you clean your tank much of this gets removed and disturbed. There is also only so much room for bacteria to grow on a flat surface. That’s why bio media is designed to have lots of surface area to grow. It’s like taking a flat surface and folding it many times over into a small space. 

We also maximize the work that these bacteria can do by placing the media in a filter. In the filter water from the fish tank is constantly circulated over the media and bacteria. This gives the bacteria easy access to all of that ammonia and nitrites to feed on. 

Types of bio Media

Bio media are made of a variety of different materials. These include things like ceramics, sintered glass, pumice stone, and plastic. While all different materials, the aim of each is to provide as much surface area as possible for bacteria. 

Where Should I Put The Bio Media In My Filter?

bio ring biological filter media in a canister filter

In order to answer this question we need to first remember the function of bio media. Bio media is a place for beneficial bacteria to colonize and consume ammonia, nitrites, and nitrates. The purpose is not to filter out suspended particles like uneaten fish food or other waste. 

This is why you should always have some type of mechanical pre-filter installed before your bio media. When I say before I mean it needs to be placed where it can filter the water before this water reaches the bio media. This way your mechanical filter will trap any of those organic particles before they get to the bio media. 

Why is this important? If you remember from our discussions above, bio media is designed to be as porous as possible. This means that those tiny pores will quickly get clogged with any type of tank crud that makes it that far. Once clogged up those bacteria will not be able to efficiently process the nitrogen waste in the water column. 

Cleaning And Replacing Bio Media

How often you clean and replace your bio media can vary somewhat based upon your specific aquarium set up. To confuse the matter more, many manufacturers recommend an unnaturally short replacement period in order to sell more media. 

Generally speaking, you will only need to gently rinse your bio media when there is waste building up on it. If you do need to rinse only do so with water from the fish tank. Chlorinated tap water will kill those friendly bacteria. If there isn’t any visible waste or build up on the media, just leave it alone. 

In regards to replacing the media this will only need to be done if the media begins to break down or it becomes totally clogged with gunk. 

When you do decide to finally replace your old media don’t change all of it at once. Instead aim to change ⅓ to ½ of your media and wait a week or two before replacing the rest. It takes a little while for the new media to become colonized with bacteria. This will ensure you will still have enough bacteria present to filter your water while the new bacteria becomes established. 

Final Thoughts On Media And Filtration

If you made it this far congrats! I hope you learned all you needed to know about biological filter media. Your way ahead of the average aquarist who just uses whatever comes with their store bought filter.