Hi there. Welcome to the forum.
You shouldnt have to add any supplements if you are using a decent salt mix.
I'd still recommend weekly pwc
's even with a skimmer. Least thats what i do.
I would wait at least 9 months for an anemone. I bought one too early myself and I brought it back after a month or so. They require a stable perfect water enviroment and excellent lighting.
As far as the clown, I really have no idea. Sorry.