<p>Biofilms, the assemblage of microbial communities on surfaces, play an important role in aquaculture by improving water quality, enhancing the growth and disease resistance of cultured organisms. Microorganisms, especially bacteria associated with biofilms, are involved in the reduction of dissolved solids and pathogens and participate in the nutrient cycling of aquaculture systems. The use of biofilm-based technology in aquaculture is considered an eco-friendly measure for the treatment of wastewater in recirculating aquaculture systems. This review paper explores the role of biofilms in improving water quality in aquaculture systems. While many microorganisms are associated with biofilms, the focus of this paper is on the bacteria community. The mechanisms through which biofilms maintain good water quality and the potential of biofilm-based sustainable aquaculture practices are discussed in detail.</p>