I had a kujaku koi in my 2000L indoor pond for about three months. He was the only big fish in that pond with a few mollies and he was friendly. Today I introduced a new kohaku to the pond and now they are both being skittish and freaking out like they are all both new to the pond. They are both around 11 inches in length. I did my weekly 25% water change before adding the new fish. How do I get my kujaku back to his calm state ? Is this behavior normal after adding new fish ? What should I do? Please help!