http://scott.aaquaria.com/videos/tigrinusfeeding.mov proves the shrimp argument ;) and he'd only been in the tank for 2 days then... But that tank gets all sorts of seafood, shrimp, scallops, clams, catfish filet slivers... almost anything... as hungry as they all are, I can never get them to eat imitation crab meat... and there's no way I'm going to the trouble and expense of real crab meat unless it's going in my stomach.
as for a good food recipe it all depends. I've made some duscus stuff that I'll never make again, had beefheart, shrimp, wheat germ, small amount of liver, spirulina, nori, some vitamins and other things I can't remember... I've since discontinued feeding beef products except a few times a month... I may make another batch with all seafood, get some catfish, whitefish and all sorts of fish, and mix it 50/50 with shrimp/scallops/clams/squid, and I may just splurge for a tiny bit of crab. I'm still going to include some spirulina, and a few other veggies. a mix isn't going to hurt carnivores... the fish or inverts they feed on have bellies full of plant matter anyway... ;) heck, I took down a shot of wheatgrass juice myself today and no vomiting or other adverse side effects.