The COREFISH project will employ a cross-disciplinary approach combining active matter physics, aquatic biology, and optical technologies to address ecological issues in aquaculture. By using a 3D fish-tracking system we will study fish behaviour under high-competition conditions and use light projections to observe fish responses to virtual microplastics. The project aims to enhance our understanding of fish collective behaviour in aquaculture and assess the impact of microplastic on aquatic fauna.