Biological filter media (BFM) is a part of your
tank filtration system made to help good bacteria grow safely. These bacteria
are a very important part of your filter. But to help them keep your aquarium
healthy, you need the best BFM you can get.
So, what are the best biological filter media? BFM can be a little complicated to
understand. There are so many different types that it can be confusing for
beginners at first. But we’ve found the 4 best biological filter media to help
you decide on the right one for your tank.
Biological filtration has been a big discussion
point for a long time. It’s a very general term that describes many types of
water filtration using bacteria. Most people only think about removing ammonia
and nitrite when it comes to biofiltration. But reef aquarists think about
lowering nitrate levels biologically too. We’ll be covering it all.
Best Biological Filter
There are many different kinds of BFM
available. Most of them are made from either plastic, natural minerals, or
In this review, we’re going to look at the best
of each to help you decide which one is the right one for your tank.
Marineland Canister Filter Bio-Balls
Marineland makes these canister filter
“bio-balls,” which are a traditional nonporous plastic BFM.
Water is able to flow freely over and through the bio-balls. This makes it perfect for supporting the type of bacteria that feed on ammonia and nitrite. However, because it’s nonporous, it can’t filter nitrate.
If you have a freshwater aquarium, with or without plants, and a canister filter, then these bio-balls are perfect for you. They never need to be replaced.
- Marineland Canister Filter Bio-Balls never get dirty
- You never need to replace them if properly maintained.
- They’re not expensive.
- Bio-balls work very well for ammonia and nitrite.
- Perfect for freshwater tanks.
- Can also be used for marine aquariums with no plants.
bio-balls cannot help regulate nitrate.
Fluval BioMax Bio Rings
Bio rings are usually made of silica and
aluminum oxide. This combination makes for a very porous biofilter media.
Fluval BioMax Bio Rings are the best example on
the market. Their internal porous system, like the Seachem Matrix BioMedia (see
below), help more bacteria to grow than smooth biofilter media do.
The ring shape allows for water to flow through
the biofilter media. This helps to make sure that bacteria are able to colonize
much quicker. Fast colonization is very important for new aquariums or if
you’ve just finished a deep clean.
Fluval BioMax Bio Rings are perfect for dealing
with ammonia, nitrite, and nitrate in your tank. It can be used in any kind of
- You can use Fluval BioMax Bio Rings as a loose BFM in canister filters.
- If you don’t use a canister filter, you can also put Fluval BioMax Bio Rings into a filter bag.
- Fluval BioMax Bio Rings are relatively inexpensive.
- Perfect for nitrification and denitrification.
- You can use Fluval BioMax Bio Rings in freshwater, marine, and reef tanks.
- Unlike other BFM, Fluval BioMax Bio Rings need to be replaced every 6 months.
Matrix BioMedia 1 Liter
The Seachem Matrix is a bio media made of solid
pumice that has been processed into 10mm pebbles. It has a rough surface, which
is perfect for bacteria.
According to Seachem, 1 liter of their Matrix
bio media gives you the same amount of surface area as 170 liters of plastic
ball alternatives. That’s because plastic balls only give you an external
surface area. Seachem Matrix, on the other hand, also gives you an internal
“macroporous” surface area.
What’s very good about this product is that
unlike other media, the macropores are big enough for nitrifying and
denitrifying bacteria. This means it can remove ammonia, nitrite, and nitrate
at the same time.
Seachem Matrix can be used in any kind of tank.
You only need 250ml for up to 25 gallons of water. 1 liter can be used for up
to 100 gallons.
- You can use Seachem Matrix in a filter bag or loose.
- Seachem Matrix never needs to be replaced.
- You can rinse the matrix without harming the bacteria.
- It removes ammonia, nitrite, and nitrate.
If you’re using a drip tray system, you may need to use a larger Pond Matrix instead.
Substrat Pro Biological Filter Media (Sintered Pearl-Shaped Glass) 1L
Substrat Pro is a type of BFM material from
Germany. Porous beads of glass are made by compressing (also known as “sintering”)
very fine glass particles together. The process of sintering determines how
porous the beads are.
Laboratories have used sintered glass similar
to Substrat Pro to grow bacteria in a controlled environment. It’s a very good
medium for this.
That’s why EHEIM decided to take the process
and make their sintered pearl-shaped glass beads for aquarium filtration.
Even though EHEIM also makes their own range of
biofilter canisters, you can use the EHEIM Substrat Pro BFM in any canister
filter’s tray. This product is best for larger canisters in both freshwater and
marine fish tanks.
beads won’t break down in your aquarium.
can easily clean the beads by rinsing them off.
ammonia, nitrate, and nitrate.
can use the EHEIM Substrat Pro in freshwater and marine tanks.
be a little expensive.
You probably have a few more questions now that
you know what the best BFM are. Don’t worry: we have the answers right here!
Do I Need a Biological Filter?
Bacteria grows everywhere in your aquarium. On
the glass, on your gravel, even on any ornaments you have in your tank.
So you might be wondering why you need a
biofilter at all if the bacteria is already everywhere. But it’s very important
for you to have one in place.
That’s because when you clean your aquarium’s
glass, rinse your gravel, scrub your ornaments, or even change lots of water at
a time, you disturb that bacteria. When your bacteria is disturbed or too much
is removed too quickly, you lose some of your natural biofilters.
Your BFM is meant to act as a safe home for the
bacteria that feed on ammonia, nitrite, and nitrate. Even if you have to do a
deep clean because your tank got neglected, the bacteria in your biofilter will
keep working to keep your aquarium healthy.
Too much ammonia, nitrite, or even nitrate can
be deadly for your fish and plants. So these bacteria are your friends. Your
BFM helps you to look after them.
After a deep clean, there’s very little or even
no bacteria left on your glass, ornaments, and gravel. Even the loose bacteria
that floats in your water is gone.
The bacteria in your biofilter makes more
bacteria that colonize the rest of your tank for you.
What Order Should I Use Biological Filter Media (BFM)?
You should always put your BFM in the cleanest
part of your filtration system.
If you don’t let water flow through your
mechanical filter first, the bigger, heavier particles will settle in and on
top of your biofilter. All the sludge and debris, like solid fish waste and
uneaten fish food, will clog up your BFM.
When this happens, you’ll have a lot of
nitrite-friendly bacteria taking over the bacteria that feeds on nitrate. This
is very bad for your fish.
That’s why you should always make sure the
water flows through your mechanical filter first. This way, you can clean or
replace the mechanical filter without disturbing the good bacteria in and on
I Use More Than 1 BFM Type, in What Order Should I Put Them?
You don’t actually need to use more than 1 BFM
type if you use a product that deals with ammonia, nitrite, and nitrate.
However, if you use something that doesn’t affect ammonia, you’re going to need
to add at least 1 more type.
In this case, it’s doesn’t really matter what
order you put your BFM in……..
If you’re using a canister filter, you can mix
the loose BFM together if you choose. The same is true for using filter bags.
Just be careful mixing 2 types of BFM, as some (like the Fluval BioMedia Bio
Rings) do need to be replaced while others don’t. If 1 of your BFM does need to
be replaced but the other doesn’t, it’s going to be easier for you not to mix
Much BFM Do I Need to Use?
This can be a little tricky to answer. Even
though some manufacturers will tell you how much BFM to use per gallon of
water, not all of them do. This is because a lot of BFM is prepackaged for a
specific type of filter.
That means there’s no one answer to this
question. How much BFM you really need depends on a lot of things. For example,
the size of your fish and how much food you give them can affect how much BFM
The best way to see how much BFM you need is to
use the amount the manufacturer suggests. Carefully monitor your ammonia,
nitrite, and nitrate levels and add more media if you need to.
Don’t know how to test those levels? Check out this guide.
Can Sponge Be Used as BFM?
While some people suggest only using sponges as
mechanical filter media, you can actually use them as BFM as well.
Link to: Other kind of MFM
You need to be careful using sponges for
mechanical and biological filter layers at the same time, though. This is
called “dual purposing.” If you are dual purposing, then you need to use more
than one sponge at the same time.
Just as importantly, you need to make sure that
the sponges you use when dual purposing have different degrees of coarseness.
You can’t use the exact same type of sponge as a mechanical and a biological
filter at the same time. This won’t filter your water properly.
When dual purposing, put the most coarse sponge
first as a mechanical filter. The finer sponges work very nicely as BFM if need
You should also be careful to clean these
sponges at different times. Otherwise, you’re going to disturb your bacteria.
Be very careful when buying sponges to use in
your aquarium. It doesn’t matter if you want to use them for mechanical
filtration, biofiltration, or both. Some sponges aren’t safe to use as any kind
Take a look at this YouTube video to find out how to see if a sponge brand is
safe for your aquarium.
How Often Do I Need to Change My BFM?
With most BFM, you don’t ever need to change or
replace them at all. As you saw with 3 of the BFM we reviewed above, all you
need to do is rinse them off.
However, if you’re using the Fluval BioMedia
Bio Rings, you’ll need to replace some of them every 6 months. Sometimes, you
make need to change them more often.
The only other time you might need to replace
your BFM is if you’re using sintered glass, like the EHEIM Substrat Pro. And
even then, you only need to change them if the beads do start to break down.
But that should never happen in a healthy tank.
Normally, even if your aquarium was neglected
and you need to do a deep clean, you can keep the same BFM.
Instead of changing your BFM, just give it a
rinse if your water flow rate is too slow. You should also rinse your BFM if
you notice that there is a lot of fish waste and dirt building up.
Never rinse your BFM
under the tap, though. The chlorine will kill all your bacteria. Instead, use
some of your aquarium water to rinse your BFM.
Do I Really Need a Mechanical Filter
and Chemical Filter if I Use a Lot of BFM?
All 3 filter types – mechanical, biological,
and chemical – are recommended. However, at the very least, you should always
have both a mechanical and biological filter in place.
That’s because they serve very different
purposes. While you can dual purpose by using sponges as both mechanical and
biological filter media, as mentioned earlier, you still need to use several
If you decide to use a biological filter
without a mechanical filter, your BFM is going to become clogged very quickly.
You should always have a mechanical filter before your BFM to prevent this from
happening by capturing all the bigger debris.
Otherwise, your tank is going to have too much
nitrite, which is very bad for your fish.
The chemical filter isn’t absolutely necessary,
but it’s always a good idea to have all 3 filter types. Chemical filters are
placed behind the mechanical and biological filters, so it’s the last filter
your water flows through.
All the things that mechanical and biological
filters cannot take care of, chemical filters do. This includes undissolved
material that can make your tank water cloudy or smell bad.
Read more at: The Best Biological Filter Media in 2019.