Piranhas are highly social, ecologically important fish whose welfare needs are poorly understood and frequently unmet in captivity and the ornamental trade.
Piranhas kept as pets are frequently housed alone, contrary to their highly social nature, causing chronic stress. Their reputation as dangerous predators leads to inadequate tank sizes and poor enrichment. Wild-caught individuals suffer transport stress and high mortality rates during collection and shipping. Many die within months of purchase due to inappropriate diet, water chemistry, or solitary housing. Even well-kept piranhas in zoos rarely receive the schooling environment they need.