I replace all evaporated water with kalkwasser - I mix RO water in a container with the Kent Marine Kalwasser mix, let it settle over night, skim the film off the top and drip it (only the clear water) into the tank over night. This replaces the calcium used by you coraline algae, snails and corals. It also helps keep my alkalinity in line.
I add a little magnesium - a capful every week(in your tank less).
I do not feed any of my corals directly, though I do add phyto plankton to the tank regularly. You don't need to do this if all you're getting are mushrooms.
I feed my anenome once a week - a dime size piece of raw shrimp. You will need to feed yours as well.
If you stick with mushrooms, green star polyps, cabbage leathers and other easy to care for corals you would just need the kalkwasser and magnesium. You don't need the phyto until you add some more intense filter feeders.
Remember regular water changes are a must in your tank.
Good luck.