Grass shrimp are pretty big and can be used to feed adult bandensis.
Quatities of live food at those prices can only be found at bait shops. i often find it to be true that a commodity thats snatches a a large price in one hobby is sold for much less in others. Fiddler crabs are an example. Id love to know of a shop that ships if you ever find one. My local bait shop carries grass shrimp, but they are easily 2-4 inches. I cant find fiddlers locally, since I dont think they are native here.
Bandensis wont go for a crab until its at least 1.5-2 months old or so. Ill throw small shore crabs in that are maybe a cm or less and the cuttles will be interested, but afraid of it.
It looks like youre realising the biggest challenge in keeping an army of cuttles. Thats keeping them fed! While trying to save yourself some $$$. With 10 cuttles eating marine shrimp, you can probably stretch out an order of 250 marine shrimp to two weeks max. Thats feeding once a day. At 65$ per 250 order, you can do the math...
My 7 month old bandensis might be to small still for grass shrimp, but I had an idea Id like to try out, since I do notice I can get them to eat freshly (Within the day) killed shrimp. This may sound a little gross, but I was going to try cutting a grass shrimp in half while alive and immediately throwing it in the cuttle tank. I suspect they will eat it as it flows through the water current. This would save me a lot of $$$ since grass shrimp at my local bait store is 3 dollars a 1/2 lb! Ill report my results soon.
Another member has pointed me to this artical
Advanced Aquarist
comparing fresh and marine inverts in regards to nutrion. It looks as if theres not too much nutritional difference between the two. Ive contemplated changing to freshwater ghost shrimps as a main diet because they are a little cheaper.
Although I think its a good idea to feed a ceph marine food only, I dont know if its absolutely necessary. Although Ive read that it may make your cephs a little more lethargic. Ive kept octopus for its full life on fiddler crabs. And many people use salt water mollies, which although live in salt water, Im sure the nutritional value is the same as the freshwater counterpart. Im sure a good mixture between the two is the best econimical and healthy choice.