Fish nipping at zoa frags #(*& %#$*%

Help!!  My fish keep nipping at my zoa frags until they succeed in pulling them off the frag plug.  Anything I can do about it????  I don't have a large set-up, so I don't have a frag tank - but then I only make a few frags at a time.  But half the time I make the zoa frags, it seems that the fish nip the polyps off.  I use the super glue gel, and I'm sure there is enough glue on the frag.  I've tried 'hiding' the frag - shaded under a rock but they find it.  I've tried covering the frag for a week with a piece of bridal veil - but as soon as I remove it, they attack it.  Any thoughts other that getting a frag tank?  How simple can one go with a frag tank???

 

I'm really not sure which fish is doing this.  I think its either the yellow tang tangs or the coral beauty.  I never actually see it happening, but the plug is constantly being tossed a couple of inches from where I placed it, and often then it is upside down.