Loaches are too active for fighters who are used to being a solitary fish. They also nip.
Your tank size will depend on the size of the cory as a group of 6 minimum is best and if you want to see them as they should be. If its big enough there are a wide range of cory that are colourful - you are best to google and have a look. Some of the ones we have are panda, sterbai, julii, adolfi, peppered, bronze, emerald green. Pygmy are small, but you will need plants to deter the fighter from nipping at them.