Aquarist Atlas is a free, research-grade guide to aquarium fish, their native waters, and keeping them in aquariums. Designed for curious beginners and experienced aquarists alike, it organizes species around the lakes, rivers, and drainage basins where they live, helping readers understand fish in their natural context. The atlas documents more than 16,700 species across 22 fish families and 32 water bodies, including cichlids, catfish, tetras, plecos, loaches, killifish, and many others.

Its species pages connect scientific and common names to cited, authoritative sources, while place-based tools let visitors explore fish by region, waterway, and size. The site also offers a world map, fish health guidance, a name thesaurus, and links to clubs and societies. Guides address questions ranging from basic care and illness prevention to breeding uncommon species.

Aquarist Atlas presents itself as an open learning resource, with articles that point to further research rather than replacing it. The service is free to access and aims to make reliable aquarium information available to everyone