Studying How to Minimize Nutrient Waste while Maximizing Macroalgae Biomass; A Vertical Method Study on An Integrated Aquaculture Recirculating System

Integrated multi-trophic aquaculture (IMTA) has been highlighted in terms of the placement of species in nutrient distribution areas. Similarly, the feeding rate in monoculture system can be complex and threaten aquaculture sustainability. A study was conducted with the different feeding rates (5%, 7.5%, and 10% day-1) on the rabbitfish Siganus guttatus in an IMTA system. The system included the green mussel Perna viridis, sea urchin Diadema setosum, and seaweed Kappaphycus alvarezii, which was grown vertically. The aim was to evaluate the ability of K. alvarezii to remove inorganic nutrients produced from feed waste at each feeding rate. The 42-day experiment showed that K. alvarezii removed total ammonia nitrogen (TAN), dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (DIP) nutrients, above 95% for all feeding rates. There was no significant difference in nutrient removal efficiency between the feeding rate levels (P>0.05). However, the biomass of K. alvarezii increased with higher feeding rates with a significant difference (P<0.05). The capacity of vertically reared K. alvarezii optimally to reduce the concentration of nitrogen and phosphorus compounds. This shows that this algae cultivation method can effectively manage fish feed waste in a multi-trophic cultivation system.