this is how my 14" channel catfish died. i bought 18. every single one of them had parasites. lucky i didn't use them all but the all had parasites and infected my catfish and ended up killing him.
I buy a whole fillet for about 3.50 - 4 bucks. Take it home and pre cut it up into different packages and freeze them. Then each day or every other day, thaw one out and presto.