Either activated carbon or chemipure is fine, in fact a good idea, to run with anemone. Supplements should be used only if you are testing for what you are adding. Alkalinity and calcium are commonly added supplements, but again, make sure you test before you add. If you do 10-20% water changes with a good quality salt, e.g., Instant Ocean or Reef Crystals, etc., then you will probably not need to add supplements. And yes, water changes are a good idea. Unless your source water is in good shape, you will want to use RO/DI water.