ok too many variables but lets just say that all i am concerned about is how long an internal parasite can live outside of its host. thats why i was considering PAM just incase any endoparasites are waiting for a new host to show up. the PAM would kill them and i would have nothing to worry about. but i dont think that they could survive without a host for long so even if i just let the tank sit empty for a month then i should be safe?