How do propagation facilities ensure they don't get all these pest in their systems?
HAHAHA...funny. Most don't. I know of only a couple "frag farms" that quarantine and/or treat yearly for red bugs. It's too expensive and risky for many frag farms to perform. What's worse are mari-cultured corals...they often have these pests.
Pest control is a serious issue in this hobby, and thankfully our area hasn't been hit yet too terribly badly. I know of a few cases of redbugs in the area, and I got monti-eating-nudis this time last year in quarantine (which is why I heavily recommend a QT tank.) I haven't heard of any AEFW (acro eating flatworms) in the area yet...knock on wood.
If there's more interest in pest control, I wrote a few articles in the old Reef Briefs on it. If we want to continue this, I'll split this thread...and we'll talk forever on it.