If your talking about White clouded mountain minnows? I know a bit about them :) They like cooler water but can be kept in higher temps. They are a shoaling fish so 5 is minimum They can be a bit nippy but mainly leave bettas alone. They like a current in the water as there from fast streams. They breed quite easily if in the right conditions. Females are plumper and males and smaller and thinner.
Do you mean the feeder rosy red minnows? They tolerate 50-80 degrees farenheit. A ten gallon could hold one male and 3 females. They breed like cichilids, and are very cool fish. They just need caves, to lay eggs and stake out territory.