Thank you guys for your responses. Just to give you an update on the situation: I put a divider between the tiger barbs and the panda corys for couple of days. The barbs didn't like it at first (obviously, it reduced the size of their home quite a bit!). I removed the divider and changed the arrangement of the decoration the day before yesterday after a water change and surprizingly the barbs didn't even notice the presence of the corys. They are even very excited that their home grew 50% larger! Now they live together very happily. And BTW, the corys love the shrimp pellets and the green tablets I give them. They have thier specific eating habits though! they have also learned what to do in case a tiger barb decides to give them a visit! They are so funny!