GMC, my dwarf octo won't eat frozen shrimp (the kind you get from a local fish store) but has eaten tons of ghost shrimp, hermit crabs, small red crabs and snails. Every other night I throw in ghost shrimp but basically force my octo to eat other stuff on the other nights because if I put in shrimp, she just eats the shrimp.
Hope that helps. (BTW, my dwarf's mantle is about 1-1/2" and the legs are about 3" right now, and hopefully not growing any bigger)