That's actually a common problem with not only the lionfish, but lots of other fish in saltwater aquaria. People often dump their unwanted animals back into the ocean, without thinking of their native habitats and natural range. Some fish that's only found in Australia or the Philippines ends up off the coast of Florida, where it has no natural predators or anything to keep its population in check. It's too bad. Invasive species is the #2 reason for species to go extinct on this planet (habitat loss by humans is #1). The invasive species will drive many native species in the area to extinction. Just like the #1 reason, most invasive species are introduced by humans.