Sunee,
I'm new here also, but I read a hint on another forum that might or might not work. The specific one was for snails and it was to put a weekend feeder in the tank. The snails would all gather on the weekend feeder and then it could be pulled out and they could be disposed of or smushed to become fishie food. Not sure if it will or won't work for slugs, but it might be worth a try.
Good luck!
~Zanne