The effectiveness of seaweeds as biofilter for reducing wastewater nutrient and preventing water pollution from hybrid grouper culture

Wastewater generated from hybrid grouper culture needs to be managed to im-prove water quality before being recirculated or discharged in the aquatic envi-ronment. Seaweed biofilter has been proposed in wastewater treatment technology for marine fish farming. This study aimed at comparing which of these species i.e. Ulva sp., Sargassum sp., Gelidium sp., and Dictyota sp. work best to absorb nutrient wastewater hybrid grouper culture. This research utilized these seaweed as treatments and controls with three replications using Completely Randomized Design. A statistical analysis was conducted to investigate the significant differ-ences in the nutrient absorptions among various seaweed species by using ANO-VA and least significant difference. Non-parametric tests namely Kruskal-Walis, Mann-Whitney, and t-test were used with confidence interval of 95. The results revealed that Ulva sp. has the best ability to reduce the nitrogen by 80, while Dictyota sp. able to reduce phosphate generated from wastewater of hybrid grouper culture by 88. While the highest absorbtion of Total Kjeldahl nitrogen (104) and phosphate (182) that were stored in thallus were performed by Ulva sp.. Ulva sp. had the best performance and highest growth rate (1.9 d-1) as bio-filter in hybrid grouper cultivation than other species. Ulva sp. has great potential as a commodity to be used in the Integrated Multi Trophic Aquaculture (IMTA) system for aquaculture sustainability.