Clown/adding fish question??

Hey guys. I have a question about my clown. It is a large clarkee. Probably about 3 and a half 4 inches. He's basically the king of the tank and was my first fish along with a six line. I now have a harlquin tusk but am going to get rid of it. (He's eaten 2 sea hares, a lobster, 2 shrimp, and probably 20 crabs and snails..) so any who I want more fish. Tanks gotten boring. Would a be able to put a smaller clown in there with out my clarkee killing it? Also if I could get some suggestions on other happy tank mate fish that I can have. It's a 40 gallon tank. Any advice is greatly appreciated!