The last school of Corys I had was in a 100G with a couple very large Tin Foil Barbs. I suspect they, the Barbs, kept the population down. I occasionally had to extract adult Corys from a Barbs mouth with forceps.
I don't see Corys available in pet stores in my area. I am told this is due to the level of sodium in the local water supply however I do not know this for a fact.
Thank you for your insight.