Aquaponics Biofilter Types Compared

There is no single “best” biofilter

Biofilters all try to solve the same biological problem: give nitrifying microorganisms enough oxygenated surface area to convert ammonia and nitrite at the system’s actual loading rate. They differ in how they expose biofilm to water and oxygen, how easily they shed or trap solids, how much pumping head they require, and how easy they are to clean or expand.

Recirculating-aquaculture literature commonly groups biological filters into submerged, trickling, fluidized/moving-media and related attached-growth systems. The correct choice depends on the whole plumbing train, not just nominal media surface area. (SRAC 453)

Moving-bed biofilm reactor (MBBR)

A moving-bed reactor keeps buoyant plastic carriers in constant motion with aeration. Biofilm grows on protected carrier surfaces while mixing repeatedly exposes the media to oxygenated water. Reviews of MBBRs in recirculating aquaculture describe them as well suited to nitrification because attached biofilm is retained in the reactor and the moving media is comparatively resistant to clogging when solids are controlled upstream. (Shitu et al., 2022)

Strengths: high active surface area in a compact volume, good oxygen transfer, no need to manually wash packed media under normal operation, easy to expand by adding carrier within the manufacturer’s allowed fill fraction.

Tradeoffs: requires vigorous continuous aeration, media-retention screens, adequate upstream solids removal and a vessel that will not release carriers into pumps or drains.

Trickle or shower filter

In a trickling filter, water is distributed over exposed media and passes downward by gravity while air moves freely through the void space. This provides excellent gas exchange and oxygen availability but requires elevation/head and splash management. Aquaculture reviews note that nitrification in trickling filters depends on hydraulic loading, TAN concentration, oxygen, alkalinity, temperature, pH and organic loading. (Eding et al., 2006)

Strengths: naturally aerated biofilm, useful CO2 stripping, visible/accessibly media, simple gravity return when site geometry permits.

Tradeoffs: pump head, noise/splash, cooling/evaporation, distribution uniformity and solids fouling if mechanical filtration is poor.

Static submerged media

Static filters keep fixed media submerged in flowing, aerated water. They can be simple to construct and can use many types of inert high-surface-area media. Their weakness is that a fixed packed bed can become a solids trap, producing channeling and oxygen-poor zones if dirty water is sent directly into it. That makes access and cleanout design important.

Strengths: simple vessel, low moving-part count, potentially low head loss.

Tradeoffs: solids sensitivity, uneven flow, manual cleaning, risk of confusing mechanical trapping with healthy biological filtration.

Fluidized sand and packed-media systems

Fine media such as sand can provide enormous surface area, but fluidized sand filters require careful hydraulic control and can be less forgiving for a casual backyard build. Bead and packed granular filters may combine solids capture and biofiltration, but mechanical loading changes head loss and demands backwashing. SRAC’s component review covers these as legitimate RAS technologies, but their operating requirements are usually more involved than the three home-scale designs above. (SRAC 453)

Comparison for a home aquaponics system

Do not choose from this table alone. The more important design questions are feed load, solids strategy, available head, aeration reliability, service access and whether a failure can bypass the filter without immediately harming fish.

For related practical guidance, see Solids filtration basics and Cycling an aquaponics system.