Productivity Improvement of Milkfish and Seaweed Polyculture using Vermicomposting Fertilizer from Sources of Waste

Abstract

Polyculture cultivation depends on the balance of several factors. Seaweed functions as a supplier of oxygen, protection for milkfish from predators, and an absorber of the dissolved CO2 from the respiration of the milkfish. In turn, the milkfish waste was used as nutrients by the seaweed. This research was carried out in Ujungpangkah Pond, Gresik District, East Java. The objective of the study was to increase pond productivity using vermicompost fertilizer from various wastes in a seaweed and milkfish polyculture system. The treatment was using food waste, Alang-Alang (Imperata) waste, banana stems, and a combination of all wastes were used to produce the vermicompost. The polyculture system used milkfish and the seaweed Gracilaria verrucosa and was cultivated for 42 days. It was found that the highest carbon uptake (717.77 ppm/day) by G. Verrucosa was with no added organic waste; the highest nitrogen uptake (16.47 ppm/day) was with combined organic waste, and the highest phosphorus uptake (19.17 ppm/day) was with feed waste. The highest daily specific growth rate (6.21%/day) of the milkfish was with banana stem waste. The feed conversion ratio (FCR) was 1.04–1.26. This small FCR showed that seaweed could be used as an alternative feed source for milkfish within a polyculture system.