my fish chase each other without nipping and I view it as them playing.
However, my fish all have their territories in my tank and they chase other fish away. It may just be "Hey, this is my spot you darn fish, stay away".
Adding more of their kind will not always ease harrassment, it could, or the new fish might get harrassed. It is hard to say. I have two red fin tetras that love being only two. They aren't always connected at the fins [
], but they do swim together, and sleep together.
All cory cats are pretty, and VERY fun to watch. I am not sure how big panda corys get, but you always have to watch the size of the fish you put in the tank. While they look so adorable small, like other animals when they are babies, they do get bigger. Mine are almost 3 inches big. Try checking out planetcatfish.com for all sorts of species of corys. There are A LOT!