Did you know that your filter is alive? Yep, it’s true! Those good bacteria in the filter keep your aquarium clean and healthy. Without them, it would be a mess!
Biological filtration has a huge impact on water quality. The bacteria in the filter are responsible for removing nasty substances in the water.
In this article you will learn everything you need to know about biological filtration and what biological media you should use in your filter.
What is biological filtration?
Biological filtration is one of three types used in aquariums. The other two, as you probably remember, are mechanical and chemical filtration.
Why is biological filtration called biological? It’s because of the bacteria in the filters.
Live bacteria found in the filter media are responsible for removing undesirable substances from the aquarium.
The bacteria used in biological filtration are good for your tank and are actually your friends.
You need these bacteria in your tank and in your filter if you want to have a healthy aquarium.
The other two filtrations I mentioned, i.e. mechanical and chemical, are also designed to remove undesirable substances.
You might think that biological filtration does the same thing. It does in a way, but here’s the key difference: mechanical filtration contains live bacteria, while mechanical and chemical filtration don’t.
In fact, biological filtration is intended to transform one substance into another, one that will be suitable for your aquarium.
Everything is really based on the nitrogen cycle. I won’t go into detail about the nitrogen cycle here because there’s another article about it.
I will only mention that fish poop and uneaten food breaks down and release ammonia in the water.
The bacteria in the filter change harmful ammonia into less harmful nitrites. Then, different bacteria change nitrites into nitrates.
It is not without reason that these bacteria were called beneficial bacteria. You need and want these bacteria in your aquarium.
Sufficient numbers of beneficial bacteria will consume the ammonia and nitrites that are produced.
This helps keep your tank’s ecosystem balanced. But, in a new aquarium, these helpful bacteria aren’t there yet. So, where do they come from?
Bacteria start growing when they find a good environment.
To make this happen faster, you can use bacterial products that you just add to water or aquarium filters.
Your task is therefore to create appropriate living conditions for individual strains of bacteria.
They need the right surface and plenty of nitrogen compounds to grow.
Just like the mechanical filtration process, biological filtration also needs to happen continuously.
To do this, you put biological media in your filter that help good bacteria thrive.
Keep reading to learn about the best biological media for your beneficial bacteria.
What types of bacteria are used in biological filtration?
Before we go any further, let’s talk about the types of bacteria in your filter. There are basically two kinds: nitrifying bacteria and denitrifying bacteria, both essential for biological filtration.
Nitrifying bacteria
These are bacteria responsible for removing ammonia and nitrites from water.
They require a source of oxygen which they use to convert ammonia to nitrite and nitrite to nitrate.
That’s why it’s really important for the biological filter to keep working all the time. This way, oxygen-rich water keeps flowing through it constantly.
If the filter stops for a few hours, the good bacteria inside could die, and their leftovers can start to decay.
If you turn on a filter that’s been off for too long, it could make the tank very dirty. To prevent this, make sure to clean the filter media well before using them again, or just replace them with new ones.
Nitrifying bacteria live in different parts of the fish tank, but they do the most good in the filter media. In the filter, there’s just the right amount of oxygen for bacteria like Nitromonas, Nitrospira, and Nitrobacter to grow well.
Nitromonas bacteria eat ammonia, converting it into nitrites. In turn, Nitrospira and Nitrobacter bacteria eat nitrites, converting them into nitrates.
Bacteria work together and one bacterium provides a food source for the next one.
Of course, in a new aquarium there is not enough of these bacteria to remove harmful substances from the water.
This is why you need to cycle your tank. The process of cycling in the aquarium causes these bacteria to multiply and their numbers increase. As the bacteria increase in number, they can start eating up the harmful substances like ammonia and nitrite in the tank all the time.
The development process of such bacteria takes several weeks . However, after this time you can be sure that the tank has been completely cycled.
It’s important to know that nitrifying bacteria arevery sensitive to chemicals. So, avoid washing filter sponges and other biological media with tap water or using chemical agents.
Nitrifying bacteria grow best on media with a large surface:
- bio balls
- filter floss
- ceramic noodles
- sponges
Denitrifying bacteria
This types of bacteria change nitrates into nitrogen. They exist wherever there is no oxygen.
In order for them to develop, there need to be areas in the tank without much oxygen. These spots usually form naturally in the bottom layers of the tank or in calm water.
Usually, there aren’t enough of these spots in your aquarium to clean the water efficiently.
However, you can use filter media that are suitable for denitrifying bacteria:
- Volcanic rock
- Ceramic noodles
You can also build a denitrifier in your aquarium. It’s pretty easy to do. The simplest one can be made by rolling up a several-meter-long hose with a diameter of about 0.4 inches.
It’s better to attach the hose to the filter’s outlet because the water there has less oxygen since aerobic bacteria inside the filter have used some of it up.
After a few days, an oxygen-free zone will form inside the hose. Bacteria settle there and will soon begin to remove nitrates from the water.
Initially, keep the water flowing slowly.
Generally, in the case of freshwater tanks, denitrifying bacteria are not so important in your aquarium.
Nitrates are not as harmful to fish as ammonia or nitrites. By changing the water regularly, you remove excess nitrates from the aquarium.
Water replacement as a method for managing nitrate levels is the best substitute for the use of denitrifying bacteria.
For saltwater aquariums, denitrifying bacteria are necessary. This is because marine fish, invertebrates and corals have a low tolerance to nitrates.
What is the best biological filter?
If you want to achieve the best possible biological filtration, you should invest in appropriate filtration media. They provide the essential surface area needed for beneficial bacteria to colonize and thrive.
In fact, the larger the surface to which bacteria can attach, the better biological filtration we can achieve.
Think of filter media as a kind of real estate for beneficial bacteria in your aquarium.
Just as a larger house can accommodate more people, filter media with a larger surface area can host more beneficial bacteria.
It’s the same here. The larger the surface area available in your filter media, the more space there is for beneficial bacteria to colonize.
By selecting the appropriate media, you’re effectively creating the best possible living conditions for the beneficial bacteria.
Below I present the most popular biological filter media.
Ceramic rings
They will work well for both nitrifying and denitrifying bacteria.
These are nothing more than unglazed pieces of fired ceramics. Most often they are white, but they can also be found in colors like cream, gray or brown.
Ceramic rings have small holes and pores on the outer part, as well as a central hole running through the entire thing. This structure means that water flows not only over them but also through them. We can also come across other names such as ceramic noodles or bio-rings .
My favorite filter material is Fluval Biomax . I have it in my Fluval filters and am very happy with it. For these rings, the central hole is slightly narrower than standard ones.
https://www.amazon.com/Fluval-Biomax-Bio-Rings-ounces/dp/B000HHSG5M
Nevertheless, they will fulfill their role effectively. Just rinse them once every few months.
They will work not only in Fluval filters but also in others. However, please remember that they are very large and will not fit in small filter media baskets. Before choosing, check the size of the filter media you wany buy.
I can also recommend Siporax. It is made in Germany and may look like any other ceramic ring but it is actually made of sintered glass.
Siporax is an ideal home for the growth of denitrifying bacteria. Remember that denitrifying bacteria take time and it may even take several months for the water in the aquarium to stabilize.
In one of my tanks, after 4 months, the amount of nitrites dropped from 10 ppm to 0 ppm after using Siporax .
sera Siporax Professional 15 mm 1, 000 mL, 10.2 oz. Aquarium Filter Accessories
Ceramic balls
Ceramic balls are suitable for both nitrifying and denitrifying bacteria.
This design significantly increases the surface area available for beneficial nitrifying bacteria to colonize. The right amount of bacteria will reduce your water changes by up to half.
Ceramic balls are perfect for a tank that is crowded.
Of course, this is not an ideal tank. But in less-than-ideal situations, like overcrowded tanks, the role of beneficial bacteria becomes even more crucial.
The more beneficial bacteria there are, the more efficiently ammonia and nitrites can be converted.
In my opinion, the best ceramic balls are MarinePure. Each ceramic ball can hold up to 240 square feet of surface area.
You can throw ceramic balls not only into the filter but also directly into the tank. Both methods are effective and will affect water quality.
However, I prefer to place them in a filter because they will not spoil the appearance of your aquarium.
CerMedia MarinePure 1.5-Inch Sphere Bio-Filter Media for Marine and Freshwater Aquariums, 2-Quart
Bio balls
Bio balls are best suited for nitrifying bacteria.
Bio balls are nothing more than plastic biomedia with an open structure.
The design of these balls may catch the eye, but it’s purposefully designed to enhance the surface area of each one.
Their unique design, which typically includes numerous holes or a lattice-like structure, significantly increases the available surface area for beneficial nitrifying bacteria to colonize.
Some balls contain small pieces of ceramic or foam hiding inside, which further increases the surface area where bacteria can adhere.
Moreover, their design allows water to flow freely through them, creating an oxygen environment for the development of bacteria.
They are best suited for external filters where we have a large basket for filter media.
To prevent waste accumulation within the holes of this medium, it’s crucial to incorporate a mechanical pre-filter.
My favorite bio balls are Marineland Bio-Filter Balls. They will work not only for mainland filters but also for others. I used it in a fluval filter and was very pleased.
Moreover, they are very easy to clean. Just submerge them in the aquarium water and the dirt will flow out by itself.
Marineland Bio-Filter Balls, Supports Biological aquarium Filtration, Fits All C-Series Canister Filters 90 Count (Pack of 1)
Moving bed filtermedia
They are suitable only for nitrifying bacteria, just like bio balls.
These media were created for a specific type of filter, namely a moving bed filter.
You have probably noticed that these media have a small surface area compared to the others I described earlier.
There’s a rationale behind this. Typically, you focus on ensuring that the bio media provides as much surface area as possible.
However, you do not focus too much on how much flow this surface receives.
In this case, these filter media have a smaller surface area than, for example, ceramic media, but more surface area is exposed to a higher flow.
This, in turn, causes the bacteria to be exposed to more nitrates, making the setup more efficient.
We can also achieve very good results with this filter medium.
K1 Filter Media PREMIUM GRADE Moving Bed Biofilm Reactor (MBBR) for Aquaponics • Aquaculture • Hydroponics • Ponds • Aquariums by Cz Garden Supply (1 Gallon)
In conclusion
Proper biological filtration has a huge impact on the health of your aquarium.
It’s one of the essential aspects of filtration to consider when setting up an aquarium.
If you don’t take proper care of your bio media, the beneficial bacteria there will simply die. Remember to use tap water for cleaning, as its chlorine content can harm these good bacteria.
What type of biological media do you use in your filter? Share your experiences in the comments below.
