Determining of water bioremediation dosage in recirculating water system for Cantik Grouper (Epinephelus fuscoguttatus × Epinephelus microdon) nurseries

Abstract

The use of recirculating aquaculture system (RAS) in nurseries of cantik grouper (Epinephelus fuscoguttatus × Epinephelus microdon) has the potential to make the culture environment more stable and maximize production perfomance, but the work of RAS decreases with the accumulation of waste in the water used. Remediation of water with microorganisms (bioremediation) can improve the performance of RAS. This research aims to determine the best dose of commercial probiotics in water bioremediation to be used in nurseries of cantik grouper seeds. This research was conducted for 7 days using a completely randomized design with four treatments and three replications. Treatment doses of probiotics tried: 3 ml/m3, 6 ml/m3, 9 ml/m3 and 12 ml/m3. The container used was a concrete tank measuring 1 m × 2 m × 0.8 m filled with 1 m3 of seawater and 3.2±0.3 cm of cantik grouper seeds with a density of 500 fish/m3. The addition of probiotics up to 12 mL/m3 had no significant effect (P>0.05) on the survival rate of cantik grouper fish for 7 days of rearing, ranging from 99.1% to 99.3%. The best results of the bioremediation process were obtained with the addition of 6 mL/m3 probiotics with the lowest range of ammonia and nitrite about 0.0896–0.9303 mg/L and 0.0977–8.4880 mg/L. The addition of a probiotic dose of 6 mL/m3 can inhibit the growth of pathogenic bacteria such as Vibrio spp. in water at the beginning, middle, and end of maintenance reached 2, 48, and 140 CFU/mL.