Agreed. Stocking is not just about the quality of the water. You also have to consider the 'comfort' of the fish; they need room to behave naturally and grow.
I keep tiger barbs, and cories ar not suitable tank mates, even if you do move the convict out (which you should as a matter of priority). They're just too boisterous and, even if they don't actually nip the cories, they tend to keep them from coming out, apart from to feed.