first of all, what are you wanting to dose for? Mag, Alk, Cal???? if you are wanting to dose anything, make sure you have a test for it...and truthfully in a cube as long as you keep up on water changes, i doubt youll need to add anything,, most of the salts have a good amount of trace elements that your normal fish and small assortment of corals need, unless you have a tank full of LPS & SPS then you may want a calcium reactor or to dose Kalkwasser (?) if your corals are taking in more than the water changes account for...