What is The Best Bio Filter Media For Freshwater and Reef Tanks

When it comes to bacterial filtration, some of you might be left scratching your heads. However, it isn’t as complicated as you might be led to believe. Bio filtering is when you let living creatures filter out the harmful microbes in your tank. It’s as simple as that! The bio that is referred to in the biological filtration media is the organic matter that you need for the bacteria to form living colonies in which they can do all their work.

This will not be a matter of finding any old material, certain organic devices encourage the best possible growth from your bacteria. In this article, while covering the removal of bacteria, we will mainly be concerned with ammonia and nitrate, both of which are very tenacious and can be quite difficult to remove using the normal methods. There is a complex system of bacteria in which ammonia is converted to harmful nitrate which is then converted to harmless nitrate by other bacteria.

What You Need To know Biological Filter Media

When it comes to your biological filter media, along with the material that you will introduce into your tank to encourage the thriving growth of a lot of this bacteria. You’ll also want to be sure that you are using the right biofilter matter to make sure that there are zero harmful nitrates in your fish tank that can actually be very harmful to fish.

So, where can you find the right biofilter media for your tank? What materials are the best to encourage the healthy growth of bacterial life in your tank? What features should your biofilter media have to give you the best performance and health for your fish? How much should a box of biofilter cost you?

Well, if you want the answers to these questions and a whole lot more, then you should keep reading. We’ll walk you right through the process of biofiltration and how it works. We’ll also talk about the best type of media for your fish tank and how you can reduce the introduction of harmful nitrates.

Best Biological Filter Media Reviews


This first media is made from silica and aluminum oxide and will form a porous ring in which all your bacteria can thrive and grow, contributing positively to the general ecosystem of your tank. This has an internal pore system that will promote the healthy flourishing of denitrifying bacteria - introducing the Fluval U Underwater Filter Biomax.

This great product gives you everything that you need for a healthy promotion of a natural balance of ammonia and nitrates. The Fluval rings do their best to cultivate the different types of bacteria that will allow natural water movement through the hole in the center and encourage bacteria to cling on.


  • The shape - these O-rings allow more water to circulate through them which will be very important for growth both inside and out by increasing the contact time that bacteria will have with these rings.

  • These come in a handy bag that allows for more accurate measurement when pouring the media into the tank itself.

  • The price - this is a very cheap bio media, perfect for newbie fish tank owners that don’t want to spend that much money.

  • This will quickly establish a solid process of nitrification, perfect for establishing a harmonious balance of nitrates and ammonia in your tank.



This next bio media filter is something a little in terms of material, made from a porous foam matter that will also help you circulate your bacteria, which will, in turn, maintain the ecosystem in your tank. This foam is cut specifically to fit the shape of most tanks, with a prefilter that you can use to capture the heavier debris of the tank.

This foam is extremely cheap to buy and is great for pretty much any tank. You can cut it in any number of shapes and you won’t have to worry about shelling out a few dollars to replace them frequently. This is best suited for freshwater aquariums, as the salt can often damage these foam pads.


  • Cheap - you can get plenty of these for a very cheap price, giving you everything that you need for a decent cleaning system.

  • This has a very large surface area that will give your bacteria plenty of space to flourish. This is good for not only ensuring the maximum bacteria growth, but because of the shape of the foam, it will preserve more space.

  • This is one of the easiest foams to clean, all you have to do is either remove the foam and wash it in foamy water or discard the whole thing and replace it with a brand new one.


  • These do tend to collect lots of grime, which can result in them becoming dirtier a lot quicker than a lot of other bio-media.

  • This can only be used with Fluvial filters which will limit you somewhat.

How To Remove Aquarium Bacteria

In any fish tank, there are literally hundreds of different types of microorganisms living in your water - it is almost an unavoidable occurrence, however, it is not always necessarily a harmful one. These organisms break down harmful bacteria and convert them into various harmless substances.

When it comes to the removal of bacteria, we’ll mainly be discussing ammonia and nitrate, both of which are very harmful when it comes to your fish. What happens is simple: the organisms in your tank will break down your ammonia until it becomes nitrate. However, the process doesn’t stop there.

Nitrate Removal

This nitrate is very harmful to your fish and needs to be consumed by other bacteria, who will then turn it into healthy and harmless nitrate. The bacteria in this tank will often convert nitrate into a healthy energy source, which it then uses to survive. The harmless nitrate that is produced will often be a byproduct of your organism’s metabolism.

The bacteria that produce the nitrate are called ‘nitrifying bacteria’ and the process that they use to produce this nitrate is called ‘nitrification’. There are other forms of bacteria that ‘denitrify’ the nitrogen into nitrogen gas. Reducing nitrate levels is a very important method of keeping your reef healthy and sustainable.

So, we hope that this has helped you understand the complicated system of nitrogen conversion. Now, let’s have a look at what happens to the bacteria once they undergo this level of nitrate exchange.

Best bio filter media

What Happens To Bacteria During Bacterial Filtration?

There are a lot of myths circulating on the internet regarding the nitrification process, a lot of which, unfortunately, is not true. However, this does not prevent rumors from sticking to the fish world like scum on the side of a tank.

One of these false theories is that nitrifying bacteria need oxygen to survive. This is not true. In nature, the oxygen levels of the environment rise and fall with the tides - and the bacteria have learned to adapt to those changes. Another rumor will have you believe that the biomaterial in your tank will require a lot of oxygen to sustain the bacteria for them to get rid of ammonia and nitrate. Again, quite the opposite is true.

All you need is a natural amount of oxygen that occurs in the environment and the natural movements of the ocean. So adding oxygen to the water will not be necessary, as there will only be a certain amount that your bacteria will be able to process. One rumor that you might have heard which is partially true is that some species of bacteria are only found in saltwater. Some species of bacteria thrive only in sea or saltwater, however, there are plenty of bacteria that can live adequately in both types.

Does Nitrate Bacteria Only Grow on Bio Filter?

Another rumor we’d happily squash is that nitrifying bacteria only thrive on bio media. This is untrue, and plenty of bacteria that ingest nitrogen can live on practically any surface - including the glass walls of your tank. This is what accounts for the build-up of green scum on your tank when you do not clean it out. It is just waste matter from your bacteria.

One fact that is true is that nitrifying bacteria need low levels of oxygen to convert nitrates into nitrogen gas. This is because this type of bacteria has evolved in low oxygen scenarios, so this is where they can best process the nitrogen in the surrounding tank. However, there are species of bacteria that will still function really well in very oxygenated water too.

Some people believe that the more surface area in your bio media then the more biological filtration will occur - this is false also. The number of bacteria that grow in your biofilter will all depend on how ammonia-loaded your aquarium is. If you have extra bio-media then you can be certain that you’ll just have more space to grow your bacteria, but not necessarily more bacteria overall. The simple fact is that bacteria will grow on pretty much any surface in your fish tank.

The biological filter should be seen as not a specified area, but rather the whole area of your tank, including the glass, gravel, rock, plants and bio-media that you might have produced especially for the growth of bacteria. Now the question that you might be asking yourself is: why the need to buy a specialized product that markets itself as bio-media? Well, this we’ll cover in the next section of the article.

Why Biological Filtration?

As we have mentioned earlier, bacteria will simply grow on every spare inch of your tank. It will form colonies that will be super helpful to your fish, processing some of the more harmful nitrates that can build up. You’ll want to make sure that their environment is not that disturbed very often. If you are cleaning your tank constantly, then you can eventually expel a buildup of some of these noxious nitrates.

This is why you should make sure that if you are going to scrape your gravel or the glass sides of your tank, that you’ll need to make sure that the bacterial balance of your tank is not that disturbed, as this will reduce the efficiency of the biofilter itself. This biofilter relies on the bacteria in your tank being relatively undisturbed. They are essentially a colony of bacteria that will need to process all of these harmful nitrates. They will also grow other bacteria that will help you to do the job of nitrate farming also.

If you have a tank that contains a few goldfish, then you’ll want to make sure that there are plenty of bacteria in your tank to filter out all the ammonia and harmful nitrate. If you own cichlids or koi carp, then you can also expect your ammonia levels to skyrocket. This is why having an additional level of bio-filter will be very important when it comes to giving you a very stable environment for your bacteria in which they can thrive. If you have a lot of live rock in your aquarium, then you’ll only need to have media that is designed for denitrification.

However, if you have fewer fish in your tank, then you won’t need that much biofilter media. If you are loading up your aquarium with biofilter material, then you might find that there is not that much more room. More bio-media doesn’t necessarily mean more bacteria. Now that we’ve explained a little more in-depth the idea of bio-media and what it should be used for, let’s move onto biological filtration and how you can use it to improve the overall state of your tank.

How Do You Use Biological Filtration?

The best way of using biological filtration is by allowing the water to flow through it naturally and organically. Unwanted and potentially harmful ingredients such as organic matter, uneaten fish food and fish waste will drift through the media. This is why it is classed as a filter, removing a lot of gunk and debris from your tank.

As your waste matter drifts around the tank, the bio-media will gradually collect it, the coarseness of the material collecting the matter slowly but surely. The heavier the matter, then the quicker it will settle on the bio-media and the more of it will get caught up in the filtering process. This organic material, once collected in the mesh of the bio-filter, will encourage the matter to grow a lot quicker. The quicker the bacteria grows then the more efficient and speedy the recovery of the matter will be. 

However, the one downside is the balance of the different types of bacteria can shift dramatically, causing the nitrifying bacteria to become outweighed by the other forms of bacteria. The best place for you to put a biofilter is in the cleanest part of your tank. This will reduce the number of bacteria that will build up.

Use nets and sponge pads to keep the levels of your bacteria very low, so that the smaller matter will be able to move more freely through the filter itself. You can rinse and replace the pre-filter media while taking care to leave the original biofilter material on your media undisturbed. Next up, we’ll be looking at how much biological filtration that you actually need. As we said before, more surface does not always equal more bacteria, so make sure that you get a quality filtration system rather than one that covers the whole tank.

How Much Biological Filtration Media Do You Need?

The thing with store-bought bio-material is that some brands often won’t come with any instructions, so you’ll have to be careful with how much you introduce into your fish tank. You must also check if your media is targeted at a certain filtration system, as this can determine which product that you end up buying. However, there is no one predetermined method for adding your media to your aquarium, it is not a precise science, you’ll just have to use your common sense.

This will all depend on how many invertebrates you have in your tank as well as the size of the fish and how often they’ll be feeding. The amount of food that you put in your fish tank will ultimately determine the levels of ammonia and nitrates that your fish produce. If you have a lot of fish then you can expect a large amount of ammonia and nitrates to be produced. A good rule of thumb will be to add a very small amount of bio-media and then start gradually increasing it and see how much it affects your tank.

What Is Best Biological Filtration Media? (Conclusion)

You can get bio-media from lots of different sources, you can go to the nearest freshwater stream and collect various pebbles, rocks and stones to put in your tank. This will come with their own system of bacteria that will respond to your fish in their own distinctive ways. 

If you have some pre-cultivated bacteria, this will get the whole denitrification system working a lot quicker. We would recommend that you start with some fresh ceramic-based materials and a wide variety of rocks for a greater mineral palette. You can even use plastic and metal in your fish tank. These come with a wide variety of minerals that will certainly stimulate the growth of your bacteria.

That’s the great thing about microorganisms - they can spring up anywhere and give you everything that you need to keep your tank nice and pollutant-free. Now that we’ve covered how the whole system works, we’ll be taking a look at some of the best bio-medias that you can currently buy online.