I have a clarkii fish and i got another one last week. I just put him in the tank with the other clarkii fish. I did have two clarkii's about two months ago but one of them died. So i brought one last week. After i put him in the tank the other one got mad. He started chasing him all over the place and goes to the bottom of the tank whips his tail around in the sand to make a hole. Is this common or not? What can i do?