CB can still have parasites. It can come from live fish, and a number of other food sources if you're not careful what you feed them. All it takes is to swallow a very tiny egg and since their food is raw, that can happen easily. Even raw fish meant for human consumption can have worm eggs in it. Doesn't hurt us 'cause we cook it. Whatever you feed them, if it's frozen at very low temperature for 90 days or so, the parasites or eggs won't survive.