fuge's really help with export...aggressive skimming along with cleaning your collection cup twice a week will help...we ran a DSB in our old tank and it helped a bit...as you saw when you saw our setup were running a denitrator...it was expensive, but it brought our nitrates from a steady 10 to 0 in about 4 weeks...we do about a 20% WC every month and everything stays happy..heres the link to the company we got the denitrator from if you want to read more on it:
http://www.midwestaquatic.com/PRODUCTS/sulfur_denitrifier.htm