Take a look at the number of dorsal spines on your cory. Sometimes, when a shop sells something called "emerald cory," it's actually a catfish belonging to the brochis genus, not corydoras. So what you have may not be a cory at all!
Don't worry though, even if it is brochis, they act the same as cories. I have a brochis cat
(which the shop called "emerald green cory"), and it just follows my C. aenus around the tank.
Brochis cats just grow a bit bigger, and have more dorsal spines. They belong to the same family as corydoras, and act almost the same. Either way, your catfish would definitely want the company of other small callichthyidae, cories or brochis.
My friend bought three Emerald cory cats at a LFS the other day and he spent the night at my house. He put them in my 30 gallon with my Emerald cory. When they all got together, they all got in a formation and went everywhere together. Now, I'm going to buy a bunch of these guys because my friend took his home today. My Cory really liked the company! 
