I agree with Lillefish and the others. A collection of Corys is a totally differtent thing than a shoal of Corys.
Lot of them have totally different behaviour, needs than others.
Interbreeding has nothing to do with keeping enough of the same species, but a lot of them are (closely) related (f.i. Aeneus group = 14 kinds of bronze, albino, lasers, venezuela) , Elegans group, aso.)
All of these fish are social fish in need of compagnons of the same / close related species (= chance of hybrids !!!!) and have specific needs / behaviour. F.i. my Peppers will hoover around the tank searching for food, bronze mainly stay on the bottom aso. As I just said in another thread : You will be amazed how there behaviour will change in bigger groups.
If a shortage of one species they will stay together rather than being on their own, but there is nothing really social about that I am afraid. I placed a vid on the other thread as well : Try to find another species in this shoal. Think you won't find one. So this corys are giving the answer themselves I think:
http
/www.youtube.com/watch?v=cWIVCdLOImw