Any good tricks for getting out a Crab?

[Trigger Man]

So I know it's been posted how to get out unwanted crabs, but I can't find it so I need the info again. I have seen a nice dark (near black) colored crab that is way to healthy as it is around a toonie in size. I have tryed unsuccessfully to grab it out with the plastic aquarium tweezers (and it should have been easy as it was hanging out on my sps colonies both times). So now I need to resort to plan B as I think it is the culprit damaging my sps.
So any ideas that have worked for you guys would be appreciated.
Thanks,