<p>Rhodolith beds are unique marine ecosystems composed primarily by calcified algae that provide essential habitat for diverse marine organisms and contribute to sediment stabilization, nutrient cycling, and carbonate production in the ocean. The Brazilian coast hosts extensive rhodolith beds that are threatened by multiple anthropogenic activities, including mining and trawl fishing. The research investigated the structure and composition of fish assemblages associated with rhodolith beds in the Costa das Algas marine protected area (MPA), central coast of Brazil. Surveys with baited remote underwater stereo video systems (BRUVS) were performed to test whether areas with greater rhodolith density and increased structural complexity exhibit higher functional richness, density and biomass of fishes. Our results show that rhodolith density has, indeed, a positive effect on fish densities, biomass and fish species richness. This underlines the importance of rhodolith beds for maintaining functional and structural properties of fish assemblages across tropical seascapes. Management plans for rhodolith bed-hosting MPAs will need to consider the structural characteristics of beds in order to mitigate irreversible changes and ensure the long-term preservation of these ecosystems and the services they offer.</p>