Generally, the reccomended amount of LR
in a tank is 1.5 lbs per gallon. I am just over 2lbs per gallon on my big tank.
In theory you can never add to much. The problem your going to run into is swimming room for your fish. I'm not sure what size tank you have, but you dont want a tang in a 75 that has 2.5lbs per gallon in it. It would be far to crowded for the tang.
Other than that...knock yourself out.
Edit: oh...and yes you can definately add both. Infact, the LR
will be far more benificial than your Bio wheel could ever hope to be.