Bait minnows as feeder fish???

Just wondering if it would be potentially bad to feed bait minnows
(i.e. crappies, fat heads) as feeder fish to a oscar that is too big
for rosey reds but too small for comets. Also, how about the worms at
bait shops? A heck of a lot cheaper than at the petstore. I have a
strong suspicion that this may be bad (disease), any thoughts? Anyone
tried this?

BTW, I only feed live feeders as a "treat" once a week.


--Cookie