you can select multiple choices. i was probably the worst to vote because i chose, calcium reactor, wavysea, wavebox and controller. in the beginning it thought these units were 'wants'. but after using them i have found huge benefits from each one. the latest unit being the wavebox has given awesome PE on the sps, and the wavyseas give crazy flow with the tunzes on them. when i was building the setup i took the advice of Fudge to get a calcium reactor. a huge thing for me with this setup was to not have to do daily stuff aside from feeding and trying to judge if corals grew over night
so i did not want to have to dose for calcium each day. i really really contemplated getting a controller at first. i just wanted one because it was a new cool toy but after having it and seeing the benefits of it i would not go without it.