Mobilization of mica by Bacillus sp. and its effect on Nile tilapia (Oreochromis niloticus) cum holy basil (Ocimum tenuiflorum)–based aquaponic system.

Abstract

A 60-day experiment was carried out to optimize the mica dosage for the best growth of the plant (holy basil) and fish (Nile tilapia) in aquaponics. Mica is a potassium-bearing phyllosilicate mineral rock used as a fertilizer in agriculture. Four mica dose treatments of C (0 g l−1), T1 (2 g l−1), T2 (4 g l−1), and T3 (6 g l−1) were taken with equal bacterial (Bacillus megaterium) dosages of 5 × 108 CFU ml−1 in all the treatments. The experiment was performed in aquaponics units with Nile tilapia (Oreochromis niloticus) and holy basil (Ocimum tenuiflorum) stocked at 1.14 kg m−3 and 28 plants m−2, respectively. The results showed that the yield of basil was highest in T2 (365.66 ± 34.27 g), followed by T3 (362.10 ± 19.99 g), T1 (337.70 ± 15.15 g), and C (324.26 ± 16.88 g). Tilapia growth was highest in C (10.79 ± 0.35 g) followed by T1 (10.45 ± 0.12 g), T2 (10.31 ± 0.09 g), and T3 (10.18 ± 0.08 g). However, there was no significant difference in fish growth corresponding to different treatments. Thus, the treatment which showed the best compromised overall growth was T2 (4 g l−1 mica). Thus, 4 g l−1 mica can be suggested as optimum mica dose for Nile tilapia and holy basil in an aquaponic system.