I feed fiddler crabs, I disable the large claw on the males, just in case it may hurt my octopus. I go to the Asian market and buy blue crabs (my octopus is very large and can handle a 5-6 inch crab) also disable the claws. I did purchase assorted crabs from a vendor but I received many decorator crabs which went after my corals, I ended up giving many away. Some people feed shore shrimp but after ordering them once and seeing the very low mortality, never ordered them again.