Atlarium is an independent, open-source, community-led atlas and resource hub for aquarium and terrarium enthusiasts. Its species atlas covers fish, plants, amphibians, reptiles, and invertebrates, with profiles featuring habitat information, care parameters, difficulty levels, and photos. The catalog includes freshwater, brackish, and marine species, as well as terrestrial invertebrates and microlife.

Alongside its encyclopaedia, Atlarium offers practical guides and reference tools for managing aquatic habitats. Visitors can learn about water parameters, compare fertilization methods for planted aquariums, and consult product information covering fertilizers and equipment, including specifications and dosage guidance. The site also catalogs aquarium and terrarium products and equipment brands.

For community members, Atlarium features shared aquarium profiles with details about their biotope, plants, animals, and setup. Interactive species challenges help users practice identification through photo, name, origin, puzzle, and memory games, while leaderboards let players compare scores. With multilingual access and a focus on useful information, learning, and shared habitat knowledge, Atlarium brings reference material and community activities together in one resource.