I run Carbon 24/7 (run through a phos reactor) because I have a lot of coral in my tank. If you do regular water changes (I'm a one to two week changer) you should not have a problem with "trace elements" The only additives you may need to worry about is Calcium (Calcium, Alk, Magnesium) Levels and that is also determined by the amount of calcium being used by your system (softies, not much / hard Corals and Clams MUCH) Get yourself a good test kit for calcium, alkalinity, and magnesium (all 3 play a important role in calcium levels) and you can play around and see how much your system uses in-between water changes. Even if you only keep softies a good calcium/alk level will get you good coraline algae growth. Jay has mastered the inexpensive way to dose calcium and Alk and has some instructions of how to go about it. (speaking of that Jay would you send me a copy of your instructions).