As far as quarantining, Im not sure, you could give it a week or several in a qt tank to observe it and make sure any spores that would hatch do so and starve with nothing to eat. BUT, I dont know what most people do. I know the guys who buy chaeto for pods typically just shake it off in their water and throw it away afterward. Most chaeto I've seen has had some hitchikers like aiptasia and bristworms. Although I've also seen mini jellyfish which are pretty neat. Can't really advise you, maybe someone else will chime in