The mix-culture of nitrifying bacteria naturally attached as
biofilm on polyethylene media (BCN-009, 2H GmbH, Germany)
was collected from an indoor recirculating shrimp
tank with 30 PSU salinity at the Center of Excellence
for Marine Biotechnology, Chulalongkorn University in
Bangkok, Thailand. This media was porous plastic with a
10 mm diameter, 8 mm in height and 864 m2/m3 in specific
surface area. Incubation of the NOB in the laboratory at
28 ± 3°C was performed by mixing the biofilter media
from the shrimp tank with the new filter media in 30 PSU
seawater. The new biofilter media was disinfected with
chlorine before being incubated with natural nitrifying
bacteria population under selective conditions for NOB in
which 10 mg-N/L sodium nitrite was added as the sole
nitrogen source. Alkalinity in the water was maintained
between 100–120 mg/L and oxygen was continuously
supplied to the system by aeration.