What type of lighting do you have? Both xenia and mushrooms do well with ost any type of lighting, which is why they're usually recommended as beginner corals. Also I think that xenia may be clove polyps, but they're very similar in care anyway.
The xenia may/will spread quickly if it likes your tank, which is why it's all over that rock (and also why it's said to "spread like a weed"). Same could be said for the mushrooms, but they split slower than the xenia and are easier to keep confined. Both get most of their food from photosynthesis and will filter feed a bit, but it's usually not necessary to supplement food for them if your tank is established.
My xenia likes moderate lighting and moderate flow, and my mushrooms are doing well with low lighting and low flow.