Studies in Macroecology deal with patterns and processes on large scale (spatial, temporal and taxonomic) and that by definition are too comprehensive to be studied with replicated, manipulative and controlled experiments as it has been traditionally performed in Ecology. Macroecological studies are still conducted with a focus on terrestrial vertebrates and plants, while marine systems and especially freshwater systems remain little explored. The objective of this study is to highlight some advances in the fields of study of aquatic macroecology (spatial patterns of alpha and beta diversity), using fish from Brazilian streams as the object of analysis. By gathering stream fish occurrence information from large scale data sets, we found high total richness in Amazonia, Cerrado and Atlantic Forest, and found on average seven species per sampling unit, with small variation related to the identity of the analyzed biomes. Yet, species composition is distinct between biomes and we found high turnover levels within them. We will guide the reader through possible causes and mechanisms of the identified patterns.