I would not use any carbon in the skimmer or the shredded media.... They sell the Bak-Pak 2R+ for reef tanks only if that is what your doing, but you can still use it as a FOWLR
works the same.... I would not even put LR IMO
... Just let it do it's job for you... There is a 2week brake in period for the skimmer to actually work in it's full status. What size is your Tank? The reef model is only up to 60Gallon if you have a Larger tank I would suggest going with the Dual instead....