The Addition of Black Soldier Fly (Hermetia illucens) Frass as Natural Fish Feed Fertilizer

Abstract

High mortality is the main challenge in fish breeding during the larval– juvenile phase. A common solution has been the use of commercial natural feed products; however, these are often too expensive to be economically feasible. Black soldier fly frass (BSF frass), produced through the bioconversion of household waste, is nutrient-rich, low-cost, and environmentally friendly. It has strong potential as a fertilizer to stimulate the growth of natural feed for aquaculture. This study aimed to analyze the abundance and diversity of natural feed (phytoplankton) following the addition of BSF frass as a fertilizer. The experiment was conducted at the Mandiangin Freshwater Aquaculture Center, Banjar Regency, using a completely randomized design with three fertilizer treatments: A (100% quail excreta), B (50% quail excreta + 50% BSF frass), and C (100% BSF frass). The results showed that BSF frass fertilizer induced phytoplankton growth. Phytoplankton from the phyla Chlorophyta and Chrysophyta were observed in treatments A and C, while treatment B supported the growth of Cyanophyta, Chlorophyta, and Chrysophyta. Phytoplankton abundance in treatment B (50% BSF frass) increased significantly on the 5th day, from 295 cells·L⁻¹ to 2,020 cells·L⁻¹. The combined fertilizer of 50% quail excreta and 50% BSF frass promoted a more diverse and abundant phytoplankton community, with a greater variety of species and more even distribution. Thus, the addition of BSF frass fertilizer can enhance phytoplankton growth, providing a natural feed source that is applicable for aquaculture practices.