Biofilter Brush

A biofilter brush is a strand-type filter media, not a scrubbing brush. It is built from a twisted wire core that locks radially projecting nylon filaments into a cylindrical form. Installed statically inside a submerged filter chamber, it serves two functions at once: the filament mass catches and holds suspended particles, and those same surfaces become colonized by biofilm, which converts ammonia to nitrite and then to nitrate. It is commonly used in koi pond upflow chambers, vortex settling systems, aquaculture tanks, and aquarium sumps.

During operation, water flows between the filaments while the brush remains fixed in place. Unlike moving-bed media, it requires no air agitation, and unlike foam blocks it does not blind as quickly. Solids accumulate on the filament surfaces and can be removed by lifting the brush and rinsing it in pond water. Biological conversion, however, takes time to develop: mechanical capture is immediate, but full nitrification capacity builds over several weeks as the biofilm matures.

The brush should remain submerged at all times. It is not intended for use as a hand-cleaning tool or for dry applications. Protect it from freezing and avoid exposure to chlorinated municipal water during maintenance, as this can damage the biofilm.

The following table lists the standard production range for biofilter brushes. All dimensions and materials can be adjusted to match your filter chamber and water chemistry.

• Koi pond and ornamental pond filter chambers: static upflow, vortex, and settlement chambers where large-diameter media provides both solids capture and nitrification.
• Aquaculture and hatchery systems: raceways, rearing tanks, and degassing columns where additional surface area improves ammonia conversion under continuous feeding.
• Aquarium sumps and refugium sections: compact brush bundles provide biological media without the need for air pumps or rotating components.
• Outdoor water features and garden ponds with seasonal temperature swings within 5–40°C, where nylon remains stable and the open structure tolerates leaf and organic debris.
• Systems that want media that can be lifted and rinsed rather than replaced, reducing long-term media replacement cost.

Start by measuring the filter chamber. Choose a brush diameter that leaves at least 20–30 mm of open space around the perimeter or between adjacent brushes so water can move through the media bed rather than channeling around the outside. Length should allow the brush to hang from the support without touching the bottom of the chamber, preventing sludge from accumulating at the base.

Next, match filament diameter to the solids load. If the system has heavy feeding, fish waste, or visible suspended particles, a coarser filament (0.70–1.00 mm) creates a more open structure that holds more solids without clogging. For lightly stocked ponds or polishing stages, a finer filament (0.30–0.50 mm) provides greater surface area per brush and better biological conversion.

Core material follows water chemistry. Freshwater ponds can use galvanized steel or stainless; if the system uses salt, ozone, or aggressive water treatment, specify 304 or 316 stainless or a plastic-coated core. The core diameter should increase with brush diameter and length to prevent sagging when fully loaded with biofilm.

Think about packing density. Brushes can be mounted side by side, but overpacking reduces flow and creates dead zones. A practical starting point is to arrange brushes with the filaments of adjacent brushes just touching, not compressed. You can adjust after monitoring ammonia and nitrite.

Finally, decide whether a biofilter brush is the right media at all. If your filtration goal is very fine mechanical polishing, a foam block or filter sock will remove smaller particles. If the main goal is maximum biological surface in a very small volume, moving-bed media such as K1 may pack more efficiently. Biofilter brushes are best when you need combined mechanical and biological action in a simple, lift-out, maintenance-friendly format.

Biofilter brush dimensions, materials, and construction can be adapted to your filter system. When you request a quote, provide the filter chamber inside dimensions, water depth, fish load or feeding rate, water type (fresh/salt), and how the brushes will be hung. A photo or sketch of the installation helps.

• Brush diameter and length: any size within production limits; we can build outside the table range for large chambers.
• Filament diameter and density: tune surface area vs. clogging resistance.
• Core material and coating: galvanized, 304/316 stainless, or PVC/PP-coated wire for aggressive water.
• Hanging eye: size, shape (ring, loop, or two-hole), and orientation (top or side mount).
• Filament color: natural, black, green, blue, or custom for product differentiation.
• Packaging and marking: bulk cartons, individual poly bags with label, or retail-ready packaging; custom hang tags or barcode labels.

If your project requires material certificates, inspection reports, or third-party testing for export or regulatory approval, we can assist with those documentation requirements as part of the customization process.