They covered some good suggestions along this line at Sunday's MAAST meeting. There were several vitamin supplements recommended to strengthen a fish's resistance and improve overall health. Are you using any garlic extract to enhance the smell of the food and entice it to eat?

Have you tried foods such as: cyclopeeze? live brine shrimp? Artic-pods (in a bottle by Reef Nutrition)?

I read a good article recently about "teaching" fish to accept prepared foods. I'll try to dig it out and reference it here.