If flushing cat litter down the toilet is a bad idea for the environment, flushing tropical fish might be even worse, according to a new study by the University of Washington and the Reef Environmental Education Foundation, a private conservation group. Off Florida’s southeast coast between 1993 and 2002, the researchers found 16 nonnative fish species, apparently set free from home aquariums.

Biologists have long suspected that intentional and unintentional aquarium releases into fresh water are a leading cause of invasions by tropical fish, which may prey on native species or endanger them by introducing parasites. But the link had never been proved despite increased sightings of exotic species, such as a pair of Pacific orbicular batfish found at the Florida Keys National Marine Sanctuary this summer. The study ruled out the possibility that the fish hitchhiked in ballast water, because the home ranges of the fish do not overlap with shipping routes. Most of the exotic invaders—such as raccoon butterfly fish, tang and angel fish, and lionfish—come from the Red Sea and the Pacific and Indian Oceans. All are popular in the aquarium trade. The moral of the story: If you have an aquarium stocked with tropical fish, don’t flush.

A copyright article from the National Wildlife Federation Oct/Nov 2004 by Associate Editor Heidi Ridgley.