Bimacs eat mostly crustaceans. A young bimac may eat a few snails, but it's shrimp and crabs that they really like. I had no problem keeping snails in my bimac tank as soon as she was a bit older.
Also, it's not really good to feed octos just one food all the time, either. They get tired of foods (never crabs or shrimp, I think!) but mine grew tired of fresh scallop and wouldn't eat it anymore and there have been similar stories from others.
Nancy