Not incredibly rare.. but around here not common to see one pushing 18"+. Saw a big one they had at the Shedd Aquarium when I was a kid... took me almost 20yrs to get my hands on one and keep it alive long enough for it to acclimatize to captivity. My husbands prized fish now.
Notropis Lutrensis for sure, i have some in my pond with notropis Chrosomus , macropodus ocellatus, corydoras paleatus and phoxinus phoxinus
They are quick, and love to swin all the time, male are more colorate. The last winter was very cold, and the all survive, my pond it's an 33 m3 and 1,45m deep