Efficiency of Chlorella vulgaris beads in improving water quality and growth of juvenile siamese fighting fish (Betta splendens)

Water quality in aquaculture has been considered to be an important factor that influences the growth and survival of fish in nursery to growout phase. A microalga, Chlorella vulgaris is utilized to filter chemical substances to maintain optimum water quality and growth of fish. The present study was conducted to know the efficiency of Chlorella vulgaris in maintaining water quality and growth of juvenile Siamese fighting fish (Betta splendens). As nutrient utilization capacity of immobilized microalgae is higher than the free floating microalgae, the experiment was consisted of 4 treatments which were control (blank beads), low (4-5 beads/mL) (T1), medium (10-12 beads/mL) (T2) and high (15-16 beads/mL) (T3) concentration of microalgae beads. It has been found that, in the control treatment, ammonium concentration initially reduced in medium rate (1.5 mg/L to 0.8 mg/L) but become slower (0.8 mg/L to 0.7 mg/L) in later days. But in first four days, reduction of ammonium and nitrite concentration was followed by T3, T2, and T1 and from day five to seven, both were slightly higher than previous day. On the other hand, PO4 3+ showed great reduction (60 mg/L) than the other treatment tanks. Highest SGR found in algal beads containing treatments than control treatment which were recorded as 4.58, 4.61, 4.57 and 3.60 in T1, T2, T3 and control treatment respectively. Results showed that, there was no significant difference (p < 0.05) in TAN, NO2-N, PO4-P, pH, DO and temperature among the microalgae beads containing treatments but significant difference (p < 0.05) found among control and microalgae beads containing treatments. It has been recommended to study economic feasibility of using microalgae beads to maintain the water quality in commercially important ornamental and aquaculture species especially in fish and shrimp hatchery for the larval rearing.