As Brazil undergoes rapid economic growth, short-sighted political decisions can threaten biological diversity and ecosystem services. Recently, the Brazilian Congress proposed a law to allow the rearing of nonnative fish in aquaculture cages in any hydroelectric reservoir of the country. This initiative may “naturalize by decree” some of the worst invasive species in the world (e.g., carps and tilapias) as a means of developing inland aquaculture and economy. The spread of aquaculture facilities will create opportunities for fish invasions to occur throughout the country, with the risk of damaging native biodiversity, ecosystem services, and environmental quality on a continental scale. The proposal ignores ecological theory, historical and/or empirical data concerning fish invasion, including dispersal, establishment, propagule pressure, invasiveness and invasibility, and all the negative consequences that may follow the invasion and establishment of nonnative organisms. This situation inspires reflection about the future of tropical biodiversity worldwide, particularly because Brazil, like many other developing countries, possesses a remarkable diversity of fish and other freshwater organisms yet has taken some political measures that are in conflict with important conservation issues.