Abstract:
Bio filter is an essential component of the Recirculatory aquaculture system (RAS), which is an
environmentally friendly culture system used in aquaculture industry. The present study evaluated
the effect of different bio filter materials on water quality and growth performance of O. niloticus
reared in a simple recirculating system. Control treatment (CT- with no bio filter) and three
treatments using bio filters with different filter material ie: PC (Lids of plastic pet bottles), BB (bio
balls), and RT (clay roof tiles) were maintained for 35 days. Each treatment had three replicates (12
tanks). Six fingerlings of O. niloticus (1.54±0.54g) were stocked in each tank (21.6 L). CT tanks were
supplied with continuous aeration and water was partially exchanged every three days. Bio filters
were operated for 24h with no water exchange during whole period. Growth and feed performance
of fish and water quality parameters, (Temperature, DO, pH, Ammonia, Nitrite, Nitrate, phosphate,
Ca2+ Hardness, Salinity, TDS, Conductivity) were analyzed throughout the study period. Final body
weights (12.23±2.62 - 14.36±4.70g) and lengths of fish (9.10±0.73 - 9.30±1.06 cm) were not
significantly different among treatments. CT showed significantly lower %ADG, %SGR and higher
FCR values compared to that of fish in all bio filter treatments. Ammonia concentration of water in
CT was ranged between 0.57±0.04 - 1.77±0.07 mg. Ammonia-N and nitrite-N were increased during
first 7 days and then started to decrease in all bio filter treatments. However final nitrate-N in all Bio
filter tanks (PC-14.39 ±1.80 mg/L, BB-12.59 ±0.38 mg/L, RT-12.92 ±0.34 mg/L) were significantly
higher at the end of study period compared to CT treatment (1.71 ±0.15 mg/L). Conductivity,
phosphate, salinity (ppt), TDS (g/L) and Ca2+ Hardness recorded significant higher values in Bio filter
treatments. DO and pH were not significantly different among treatments. Growth performance,
ammonia oxidizing efficiency and water quality parameters of bio filter treatments were better
compared to control treatment. The results suggests that the Lids of plastic pet bottles (PC) and
Pieces of clay roof tiles (RT) could be used as an alternative filter media instead of commercially used
bio balls
