Biological Filter

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.

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.

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.

Yes — it pairs with a Roots or regenerative blower and diffusers; the constant motion keeps the biofilm thin, active and self-cleaning.

A biofloc filter (biological filter applied to a biofloc system) is not always the primary treatment in biofloc — the floc itself provides biofiltration — but a dedicated biofilter is used in hybrid biofloc-RAS systems to handle peak ammonia loads and give more stable water chemistry. SIGMA's MBBR biofilter can be added to any biofloc tank system as a supplementary ammonia-control stage.

In a RAS loop the bio filter for RAS fish farming sits after mechanical filtration (drum or sand filter) and before UV sterilization, converting toxic ammonia into nitrate via nitrifying bacteria on high-surface-area media. SIGMA offers MBBR, fluidized coral-sand bed and trickling types, selected by feed load and species. It pairs with a roots blower for aeration and plugs into SIGMA's complete RAS chain.

A moving bed bioreactor is a biofilter design where free-floating plastic carriers tumble continuously in an aerated tank, giving nitrifying bacteria a huge, self-cleaning surface to colonise. It is the most common aquaculture biofilter design today because it needs no backwash and handles feed-load swings well — a fluidized coral-sand bed or a ceramic ring filter bed are the fixed-media alternatives for smaller or lower-budget systems.