Me: Quarantine! Even if a fish turns out to be completely healthy in quarantine, you know you won't harm all of your fish. If it is sick, then you you know you won't harm all of your fish.
New Tankhead: But the quarantine is stressful, and this fish is already delicate!
Me: That's great that it's delicate, but if it turns out to be sick, you'll have to catch it and quarantine it with every other fish in your tank. That's more stressful!
So yeah, quarantine.
Someone give Matt some Karma for me, I can't.