Interesting, I know most serious Discus breeders use beef-heart as a main food. I have feed pinkies to large cichlids before without any problems. I had a juvenile prairie king snake so I had a colony of mice and always had more then I could use, so I gave them to a peacock a jaguar and some snake-heads. They all seemed to enjoy them.
Just because some discus owners do it doesn't mean it is a good idea. I would never feed discus beef hart, because they should be eating invertebrate foods like they do in the wild. There are articles out there about beef hart being bad for oscars, but many people still feed them that. I don't know, but it maybe ok to feed them pinkies once in awhile.
I don't see what is cool about feeding fish pinkies anyway. It would be messy and you would have to do a lot more water changes.
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