Cories can well survive as single fish so you can expect to see that work for you. On the other hand, cories in small numbers are far less than in optimum conditions. I kept cories in tiny numbers in the 1950s and more recently in larger numbers. In my own opinion, I see no reason to ever keep cories in small numbers again. They are just that much more entertaining with their antics when kept in groups of at least 6 and better yet 10 or more. My cories, these days, are among my favorite fish but back in the days when I kept them in 2 or 3 per species I regarded them as little more than a clean up crew. These are delightful little fish who will entertain you for hours if you have enough of a species in a tank. That is simply my own perspective though. Nobody else needs to adopt my own attitude toward cories.