Chaeto grows like a weed with 6700K. As far as the sand bed, I personally like a remote deep sand bed. You can research that subject on RC to find a strategy right for your sump/situation. As far as salt, I've heard good things about Coral Pro Salt, though I have no experience with it. You could mix some up to 1.026 and check the alkalinity, ph, Ca and see if it looks good. I would say the most important thing is that you do regular water changes. Once you get 6700K PCs, expect your Chaeoto to begin growing rapidly, most likely reducing nitrates and phosphates assuming you have a large ball of it.