The main goal of aquariums today is to raise public awareness and positively change visitor behaviour towards the environment. In addition, aquariums are becoming increasingly engaged in fish conservation programmes within their range country or overseas. The World Association of Zoo and Aquariums has developed a global aquarium strategy for conservation and sustainability. Within Europe, conservation-breeding programmes are managed by the European Association of Zoos and Aquaria, and the European Union of Aquarium Curators Fish and Aquatic Invertebrate Taxon Advisory Group. The large and growing number of species of freshwater fish under threat can make deciding which species are priorities for aquarium collections very difficult. The Regional Collection Plan is a mechanism that defines the role a species plays within a zoological collection, helping collection managers make decisions about which species of freshwater fish are prioritized for ex situ conservation management with an associated action plan used to ensure that conservation goals are realized. We present clear and demonstrable roles that public aquariums can play in the conservation of freshwater fishes and discuss the challenges for such conservation initiatives in European aquariums with the increasing trend for marine exhibits and marine-focused aquariums.