Cories will breed in any temp between 24 and 28 C in any tank. If they are healthy fish they will spawn every 2-3 weeks on the glass, plants or ornaments. I know this as I have bred cories and would like to again one day as it's fun to watch the young cories grow up. The only problem with breeding cories is that you can't just leave them in the tank as other fish will eat the eggs and raising them yourself is quite hard as I found. I started with about 30 newborn fry and only managed to raise 4 to the 1" stage.