Take frozen silversides, thaw them in tank water, then chop them up and feed them to the triggers on the end of a stick. They'll rip 'em right off.
There is also a pellet food that is NOT crap, called Thera-A from New Life. Awesome stuff, and every one of our fish love it. They're relatively heavy pellets, so they'll sink well, and they're not too large for triggers over 6 months.