How to Lower Nitrates

Hello All:
I have a pretty healthy tank right now, and introduced my first GSP.

Real quick:
92 gallons
30 lbs LR
100 lbs LS
UV sterilizer
Media Reactor with BioPellets
Skimmer
25 gallon sump
(Bio Balls... I am thinking it's time to remove these but I want advice)

I can't seem to get my nitrates below 10-20
pH is usually 8-8.1
Salinity is 1.0235-1.024
Ammonia is 0
Nitrites is 0
Calcium is 400-420
KH is 10-11
Phosphates is .1-.2

I was thinking of putting new LR in the tank or sump but I am afraid to mini-cycle the tank and hurt the fish. The LR I have and would buy is the synthetic stuff made in CA and sprayed on with the bacteria. I was thinking of buying it and letting it sit in tank water in a bucket for a period of time then introducing some in the sump and DT. And I think I may remove half the BioBalls, then all of them.

None of the life in the tank seems adversely affected by the nitrates, but the GSP (9 days old) does not come out to the extent it did in the LFS. Either way, I would like to be one of those reefers with 0 nitrates if I can.

Any advice would be great.