Then schedule a meeting. Tell him to be there early tomorrow because you need to talk, and then deliver the news face to face. Have a list of events in which he

Then schedule a meeting. Tell him to be there early tomorrow because you need to talk, and then deliver the news face to face. Have a list of events in which he didn't perform as you expected him to, explain that while he had an acceptable performance, your company is too small to survive with less than absolutely stellar work, wish him best of luck, and say you are available if he needs references. I think being nice and respectful is much more important than being informal. In fact, I think informality may give the impression that you don't care.