Imperial ID Picky eater, need help

[Blue Butcher]

I purchased, a then 17", Imperial ID in November/07. She is pushing 19" now. My problem is she eats like a pig when she likes her food. She wont let the other two larger fish eat till she is done. My supplier has stopped making one of her foods. The one I used to fill her up because the other two did not like it. They will only eat algae tablets. She wont eat beefheart, shrimp, worms. I have asked for help before and always had great responses from the other members. So here I go again. thanks for the help,