The nitrification core
Efficient removal of ammonia and nitrite sustains high stocking density and low water exchange in any RAS.
Biological Filter
The biological engine of your RAS — an aquaculture biofilter (moving-bed MBBR, fluidized-bed or trickling type) packed with high-surface bio media where nitrifying bacteria convert toxic ammonia and nitrite into harmless nitrate. Compact footprint, low power, fresh- and seawater-ready, sized to your farm's feed and ammonia load.
- FormatsMBBR · fluidized bed · trickling
- Surface areaUp to 20,000–24,000 m²/m³ (coral sand)
- BuildLDPE / UPVC / PP / FRP
- WaterFresh & saltwater
ISO 9001 CE OEM / ODM
15+ years in aquaculture engineering · Trusted by Japfa Group, Japan Nissui & Tropo Farms · Shipped worldwide in one container
Product Description
The first step in setting up a healthy aquarium is to establish a biological filter. A biological filter is a natural filtering system consisting of helpful bacterial colonies that, through a cycling process, convert pollutants in water to harmless nitrate. Nitrate is nitrogen, therefore this cycling process is also referred to as the nitrogen cycle, or cycling a tank.
Advantage:
★Remove Ammonia/Nitrogen, Nitrite, Nitrate, and Thiocyanogen in aquaculture water.
★Combining the advantages of trickling filter and activated sludge process, highly concentrated biological film with high treatment efficiency. The ammonia nitrogen conversion rate can be improved 2-4 times.
★Have double function as a biological filter and mechanical filter. And at the same time, it has functions of
backwashing, large particles discharge, and emptying.
★Compare with another biological filter, the size is smaller, with less land occupation.
★Special design for recirculating aquaculture system.
Video of Product
Application
Specifications
Models & configuration
Models and performance figures integrated from proven industry configurations — final specifications are confirmed by SIGMA's production line per project.
| Model | Capacity | Typical use | Core configuration |
|---|---|---|---|
| SIGMA-BF-MBBR-5 | 5 m³/h | ||
| SIGMA-BF-MBBR-10 | 10 m³/h | ||
| SIGMA-BF-MBBR-30 | 30 m³/h | ||
| SIGMA-BF-FSB | Sized per farm | ||
| SIGMA-BF-TRK | Sized per farm |
| Filter media | K1/K3/K5 MBBR carriers · coral sand · bio balls · ceramic rings (see Filter Media) |
|---|---|
| Ammonia handling | Fluidized coral-sand bed: ~16 g NH₄ per kg of sand per 24 h (industry reference figure) |
| Specific surface area | Media-dependent: MBBR 500–5,500 m²/m³; coral sand 20,000–24,000 m²/m³ |
| Housing | LDPE / UPVC / PP / FRP with standard UPVC pipeline connections |
| Water type | Freshwater / saltwater |
| Aeration | Requires blower + diffuser aeration to fluidize moving-bed media |
| Options | Combined trickling/degassing stage, enlarged reactor, PLC integration |
System composition
Multiple formats to match the load
Moving bed bioreactor (MBBR), fluidized coral-sand bed or trickling/submerged type — selected by feed load and species.
Huge contact area
Fluidized coral-sand beds reach 20,000–24,000 m²/m³, shrinking footprint and energy use versus a traditional bio-trough.
Self-cleaning moving bed
Tumbling carriers keep the biofilm thin and active, so the biofilter rarely needs manual maintenance.
Corrosion-resistant housing
LDPE/UPVC/PP bodies suit fresh and salt water, with standard pipeline connections for easy installation.
Supplied as a package
Biofilter, media and aeration blower can be delivered as one matched set.
Application
- Core biological stage of RAS water treatment — after mechanical filtration, before UV
- High-density fish and shrimp grow-out, nurseries and seawater recirculating systems
- Large koi-pond and ornamental-fish biological filtration
- Biological stage in wastewater / industrial water treatment
Video
Biological Filter
FAQ
Frequently asked questions
What does a biological filter do in a RAS?
It houses a large population of nitrifying bacteria on high-surface media that convert toxic ammonia and nitrite into far less harmful nitrate, so fish stay healthy at high stocking density.
What types of biofilter does SIGMA offer?
A moving-bed bioreactor (MBBR / fluidized bed) with K1/K3/K5 media, a fluidized sand-bed biofilter using calcified coral sand, and a trickling / submerged biofilter.
How is the biofilter sized?
It is sized to the farm’s feed load and species. A fluidized coral-sand bed offers an enormous contact area (up to ~20,000–24,000 m²/m³) in a much smaller footprint than a traditional bio-trough.
Does the moving-bed biofilter need aeration?
Yes — it pairs with a Roots or regenerative blower and diffusers; the constant motion keeps the biofilm thin, active and self-cleaning.
Related equipment
Related equipment
Filter Media
High-surface-area bio filter media (MBBR carriers, bio-balls) for RAS & aquaculture biofilters — fast nitrification, durable. Bulk supply from SIGMA. Request specs & a quote.
View details →
RAS system
Complete recirculating aquaculture (RAS) systems: drum filters, biofilters, oxygen cones, pumps & monitoring. Custom-designed for your species & volume. Manufacturer-direct. Get a quote.
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Automatic Rotary Drum Filter
Self-cleaning rotary drum filters for RAS & aquaculture — automatic solids removal, multiple flow rates & micron options. Factory-direct from SIGMA. Request sizing & pricing.
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Root Blower
High-efficiency roots blowers for biofloc, RAS & pond aeration. Direct-from-factory pricing, multiple capacities, worldwide export. Request specs & a quote from SIGMA engineers.
View details →Request a tailored quote
Tell us your species, target density and site — our engineers size the system and reply within one business day.
Biological Filter Request a Quote