I haven't really found a way to prevent it. I have had my go around with it, and it was a nightmare. I dip and quarantine all my corals and still ended up with it happening. From best I have learned, there are two different variations. One is the typical brown jelly disease, where you see the actually "brown jelly" which is the coral dispensing it's zooanthellae algae, and then it withers away and dies. This variation seems to only effect euphyllia species, not any other corals. The other is what I dealt with (and I believe what you're dealing with from talking to you in your other thread), where it will start with euphyllia species, but attacks other LPS if left untreated once it is done attacking the euphyllia. It's more of a bacterial infection. It appears as a white film (if any film at all) on torches and other corals, and the rapidly the coral basically melts away. I was literally loosing heads on my frogspawn and torches, etc in less than 12 hours time.
The only thing that worked for me was to remove any coral that was visibly effected and cut away any dead or dying heads. Those corals were QT'd if I thought that there was any hope of them surviving, which in 90% of the cases, they did not :-( I had to dip EVERY LPS coral in my tank in Lugols/Melafix 2x a week (my husband says 3x) for two weeks. During these two weeks, I was also adding Lugol's to the main display tank as well. If I saw any more loss during this time, I again, cut off any dying or sick heads and dipped that coral again separately an additional time.
After two weeks of dipping and dosing, my LPS seems to be fine and I don't have any more loss. It was a horrible experience to go through. I didn't act as quickly as I should have and probably could have saved more pieces if I had acted sooner. I easily lost $1000 in LPS