Montipora Eating Nudibranchs

[SmallFry]

Sometime in June or July my tank came down with the dreaded Montipora eating Nudibranchs. I tried to suck them off the corals, but they just kept coming back. As a last ditch I tossed the corals that were affected? Fortunately they were only frags so not much money involved, just lost time and irritating to loose a frag that you've grown to a reasonable size. After each coral I tossed I got a couple of weeks befor they hit the next. Finally I came to the conclusion I wasn't going to win so I got rid of every bit of montipora I had (all but two corals in the tank in fact) and figured the Nudibranchs would die out with no montipora to live on. The plan was to start restocking about Christmas. Now here comes the curve-ball...

Tonight while searching for the three purple firefish that I haven't seen since they came out of quarantine on Monday, I found a piece of montipora on the sand bed at the back of the tank and it's alive. It must've been there since I knocked it off when I pried the bigger frag off the rock months ago and it seems the Nudibranchs haven't found it.. My question is whether I should keep it or whether I should throw it away to make sure there is no food source for he Nudibranchs and then continue with my stocking plan in a couple of months?

Never dealt with these things before so any help would be appreciated.
Rob.