Jennifer,
As a reminder, if you already had Acropora in your tank, or acquired some later, you really cannot determine which colony brought the problem INTO your tank. Every species of Acropora seems to have a different level of suseptibility to them. Some (like the green Bali slimer) seem to be nearly, or possible completely immune to them. Some can be 'carriers' (hardly affected themselves).
If you only have a few colonies of Acropora, and they are not encrusted onto your rocks yet, you might be able to remove them, dip them for 6 hours or so and return them to your tank. 2-3 treatments like that, spaced a week or so apart to give the colonies a chance to recover from the dip might get them all. The bugs can, and do crawl around in the tank, so they might jump back onto your colonies each time, but I don't think that at anyone time there are really very many anywhere other than on the target colonies. Removing the colonies by though use of a container that you dip into the tank (so that the colony is never removed from the water) I think would also make it less likely that there will be any left behind in the tank when you take them out for dips.
I'm of the opinion that you can in fact get a 100% kill in a main tank with a single treatment of Interceptor if you are careful and get the dose right.
Regarding a natural predator, there is a species of pipefish that eats them (there was a video of the species doing it a while back on some site), but it's not really a very effective control in a reef tank environment from what I've read. There are quite likely other species of predators as well of course.
While a bit dated, I think my old article on these is still worth a read if you are new to the bugs.
http://www.advancedaquarist.com/issues/june2003/feature.htm