What to do with sick cardinal tetra?

Yesterday i got a school of cardinal tetras to go with my minnows in a 10gal. I just noticed one of the cardianls has white spots which is obviously ich. As far as i can see the other ones dont have them..yet. I have this little plastic betta container, should i place the cardinal there and wait for it to heal or die? or should i just treat the whole tank with ich medication? if so, what medication and when? by when i mean at which stage of the disease, right now or when it spreads to other fish? detailed answers plz. thanks