Maybe I should give you my definition of vermin: animals that reproduce in crazy numbers and live on the fringe of human societies. Often dirty, sometimes disease ridden. (fleas, feline aids, leukemia, god forbid rabies)
I have owned everything from pigs, rats, tarantulas, chickens, goats, rabbits, snakes, lizards. You name it, I have probably had it. Nothing fits my definition better than cats. I seriously do love cats, I wouldn't and couldn't have done as much for them if I didn't love them. And I am not insulting people who own them so much as the problems that people not owning them have caused for me. It is just how I view them as animals. Like I said, it is in a semi-affectionate way that I call them vermin.
Remember that the tank your fish lives in is his or her's whole world. Ask yourself this question, and answer it honestly: would you choose to live there?