Well Bbs(baby brine shrimp) is really better for fry and small fishes. That does not mean that you cant feed it to large fishes. If you are planning to feed it to large fishes or medium fishes feed then worms as you said or brine shrimp which is bigger than baby brine shrimp. You can buy it frozen and prepare it yourself. It is faster than hatching them. But frozen ones loose their nutrients over time so if you buy frozen foods try to use it all within a months time.