Okay I am a tad bit confused. Rosy Reds are bad, flat heads are bad. But minnows are ok?

Okay, when I look them up, they have rosy red minnows, also known as flatheads..

So what is actually the best fish(live) to feed? I only feed worms & pinkies. Just wondering, since Aundrea's Garter is sick, I am thinking it's the minnows she got from the petstore. Cause that is pretty much all he ate, except a few times she got him to eat a pinkie

Thank you...