A parasitic fish, dangerous to other fishes and possibly to humans-- as noted above. There are small and larger species, the large species can do this. Florida would be a favorable habitat for them and native fish would likely have no defense.
Florida has enough problems with invasive species escaped from the pet trade. Seriously, who thinks making candiru legal, then having them added to the list of harmful invasive species-- because some stupidly irresponsible hobbyist releases them (and sooner or later someone would), or they somehow escape during a hurricane-- would be a good idea! ☹