Hand holding plastic bead growth media, media bubbling in biofilter water

Biofiltration lies at the heart of recirculating aquaculture systems. Plastic beads tumble through the biofilter tanks and serve as the growth media. They provide ample surface area for bacteria to cling to and grow colonies, eventually developing into a gel-like substance known as a biofilm. These microbial communities purify the water and remove or detoxify harmful waste products and uneaten feed as water is recycled through the culture tanks.

biofilter components including growth media, oyster larvae through microscope, and biofilter tanks.
At left: Plastic beads in the biofilter provide surface area for the growth of beneficial bacteria to support the nitrification cycle. At center: Oyster larvae under a microscope at the Oyster Seed Holdings hatchery. At right: The study system offers several layers of filtration as water cycles through a heterotrophic filter, an autotrophic filter, and a protein skimmer. Photos by Keri Rouse for Virginia Tech.