A filter is critical for your aquarium. It provides a clean water column for your pet fish to live in and aids with tank maintenance. Filter media is used to provide this clean-up with biological, chemical, and mechanical filtration.
In this article, we will discuss biological media types and uses. This will be followed by reviews of some of the best biological filters media options available, each with unique characteristics:
Last update on 2023-11-08 / Affiliate links / Images from Amazon Product Advertising API
- Fluval Biomax Filter Media
- CNZ Aquarium Filter Bio-Balls
- Tetra Bio-Bag Filter Cartridges
- Fluval 306/406 Bio-Foam
- EHEIM Substrat Pro Biological Filter Media
Table of Contents
Filter media is used in an aquarium’s filter system to help promote a healthy water column. Biological media is one of the three types used in a filter, with chemical and mechanical media being the others.
What Does Biological Media Do?
A media that performs biological filtration functions as a home for different “good” bacteria that break down harmful materials in the tank’s water. These bacteria make up the major component in the nitrogen cycle.
The Nitrogen Cycle
The fish and other creatures that you keep in your aquarium release carbon dioxide and bodily wastes into the water. Food and other debris also break down over time. The carbon dioxide is removed by plants and released into the air at the water surface.
Ammonia, which is highly toxic to fish, remains in the water column. A bacteria (Nitrosomonas) converts the ammonia into nitrites. This material is also lethal to your pets and must be removed.
Nitrobacter bacteria will then form and convert it into nitrates. It is not lethal unless it builds into high concentrations. Nitrates can be removed by plants or through water changes.
Biological Media Provides A Safe Home
These bacteria form colonies that can live anywhere in the aquarium. Colonies that grow in the tank can be removed during cleaning. They can also be washed away during water changes.
Filters provide a space where bacteria colonies can safely grow without being destroyed. The best biological filter media provides an ideal surface for these colonies to grow. Gentle rinsing with tank water (instead of tap) will keep the bacteria thriving even during filter cleaning.
What Different Types of Biological Filter Media Are Available?
Ceramic Cell Pore: This ceramic material comes in a variety of shapes and sizes that can fit inside your filter.
Foam/Sponge: Pieces are inserted in the filter where water is forced through it.
Glass Balls: These are glass spheres of varying sizes that fit inside of the filter.
Plastic Balls: Similar to the glass spheres mentioned previous. They are light enough to float and help to agitate the water in the filter.
Rocks: Lava and zeolite are often used (as well as substrate materials with an under-gravel filter system).
String Mesh: This material may be densely packed into the filter in the path of the water.
How Is Biological Filter Media Used?
The process is the same no matter which type of material is used. A compartment or tray can be found inside of most styles of filters that are used to house the product. The manufacturer will recommend the proper location that the media is to be placed.
Once an aquarium is filled with water, it is “cycled” to begin the biological process. Pieces of decaying food can start the process. Products are also available that help to establish colonies.
All fish tank components must be cleaned, and that includes the filter. The bacteria colonies may be destroyed if care is not taken. Water from the fish tank is used to gently rinse or soak the media before it is returned to the filter.
A Note About Fish And Fish-less Cycling
In years past, hobbyists would use one or two cheap fish to start a tank cycle. The harsh water conditions would often kill the fish. Today, cycling a tank without fish is considered the ethical way to start the biological process.
What You Should Look For With Biological Filter Media
The large selection of designs and materials used for these products do share some common characteristics. When selecting a media, remember to consult the owner’s manual of your filter for media types that should be avoided or recommended to use.
Surface Area: More surface area provides more living space. Products that are porous and filled with holes offer this. Media material that provides a smooth surface or solid design should be avoided.
Filter Space: The size of the media can determine that amount that can be placed in a compartment or tray. Smaller pieces will inhibit water flow more than larger chunks will. Fine media clogs quickly and must be cleaned more often.
Durability: Media that breaks down must be replaced. This often means that the bacteria colonies must also be regrown. Many hobbyists will purchase extra media and begin to grow bacteria colonies on it before it replaces older bacteria housing.
Five Biological Media Reviews
Fluval Biomax Filter Media
A porous material designed to offer plenty of bacteria housing.
Each box of Biomax includes 17.63-ounces of material. This is a good quantity that can fill most filter compartments. Each ring is made from an inert ceramic that will not alter the water column’s chemical composition.
The material seems to be attractive to bacteria, as they are able to establish healthy colonies quickly. The surface of each piece is porous, a feature that is great for providing more surface for bacteria to live on. The center hole provides an extra surface as well, and also keeps water flowing smoothly through the filter.
The ceramic will begin to crumble over time, and replacements should be made at half-loads to prevent complete bacteria loss. Extra Biomax can be placed in the tank before a change-out to establish colonies as well.
- The porous surface provides more bacteria space
- The center hole lessens water restriction
- Bacteria are able to establish a foothold quickly
- Fluval’s Biomax may break down sooner than other ceramic-type media
CNZ Aquarium Filter Bio-Balls
Large and durable plastic balls that will not inhibit water flow.
Each pack of Bio-Balls weighs four-ounces and contains 50 balls. Each piece measures one-inch in diameter, a size that should not restrict water as it moves through the filter. The balls are hollow and provide a surface area on four sides of each rib.
The ribs alone would provide an average amount of space, but each one is filled with a chunk of sponge that will provide extra living quarters for bacteria to thrive. The sponge is a coarse texture and should take a longer period of time to clog from build-up.
The sponge texture should not impact water flow noticeably. Bio-Balls could be ideal for those with large filter compartments or media trays. This will allow the larger pieces to filter water efficiently.
- The plastic housing will not degrade over time
- Each ball contains sponge for extra bacterial growth
- The larger size of each piece will require a spacious filter
Tetra Bio-Bag Filter Cartridges
A disposable mesh cartridge that provides two types of filtration.
Each box of Bio-Bag comes with 12-cartridges. Tetra does offer boxes in eight as well as 24-cartridges. Each cartridge comes unassembled, which can allow a user to use the bag in other types of filter systems than they were designed for.
The fiber mesh provides a good place for bacteria to grow and can double as a form of mechanical filtration as well. Each pad is designed to be disposable, which will eliminate the need for cleaning. This feature comes at the price of losing the established bacteria colony living in the old cartridge.
These cartridges will provide a great double-filtration method for power-head filters, especially Tetra’s Whisper line.
- Each cartridge provides both biological and mechanical filtration
- The fibers can house a large bacterial colony
- It is designed to work well with Whisper-style power heads
- The product requires some assembly before it can be used
Fluval 306/406 Bio-Foam
A porous sponge filter material offers dense bacteria colony housing.
Each pack of Bio-Foam contains two pieces of course foam. The structure provides a good home for bacteria to grow while allowing water to flow through the material. A nice feature about the design is that it will double as a mechanical filter as well.
The foam will filter debris, but it can also become clogged more easily than other media types. This will require more frequent cleanings which should not be an issue for the re-usable foam pieces. The material can be soaked in tank water while the rest of the filter is receiving a more complete cleaning.
This product has been cut to fit Fluval’s 306 and 406 series filters, but it can be used in other types of filters effectively. Larger spaces may require more pieces for proper coverage.
- The durable material can be re-used
- The foam can act as a mechanical filter for large debris
- It comes at a higher price point for the amount offered – however it’s a great brand
EHEIM Substrat Pro Biological Filter Media
A glass-based biological media that provides a rough growing surface.
Eheim is a well-known German brand in the European fish-hobby. Each container holds two-liters of material (over four-pounds). It is made from sintered glass that is compressed into drop shapes of various sizes. This material offers a solid surface for bacteria to grow on.
While the compressed glass is porous, it is durable and should last with normal use. The product can be used to fill a basket or tray completely, taking advantage of the entire volume offered by the filter. A filter bag would keep these beads in place in pressurized cannister environments.
Cleaning this material should be easy and require a simple soaking in tank water. Substrate Pro would provide good biological filtration in a canister filter.
- It provides a great surface for bacterial colony support
- The beads are easy to clean
- This product can be used in almost all filters
- Price point – however it’s a great brand
All of the products reviewed above provide an adequate structure that is necessary for good bacteria to thrive. Of the five, we feel that the Fluval BioMax Biological Material Remover, 500 g - Biological Filter Media for Aquariums provides aquarium hobbyists with the best features.
- Filter Compatibility: Compatible with Fluval Filter Series 106, 206, 306, 406, FX5, FX6, 105, 205, 305, 405, 104, 204, 304, and 404.
- Water Clarification: BioMax is a premium-grade biological filter media that provides superior filtration and helps reduce and control ammonia and nitrate levels for a healthy nitrogen level in the water.
- Ideal Environment: BioMax helps create crystal clear water, making ideal conditions for fish and plants in your tank. The complex porous design ensures optimal contact time as water passes through.
- Versatile: This filter media is suitable for freshwater and saltwater aquariums. Replace monthly for best results. Please note, replenish only half the filter media at one time to allow proper seeding.
- Additional Features: Will not affect water characteristics.
Last update on 2023-11-08 / Affiliate links / Images from Amazon Product Advertising API
The surface is extremely rough, and the large openings provide plenty of growing space. The ring shape, along with the center hole, allows proper water flow. Its size will permit it to be used in most filters, and bacteria seem to establish themselves on it readily!
Fluval Biomax Filter Media Review
Ease of Use