I'll let you guys in a little trade secret.......nitrates aren't as bad as many think. Especially in an all fish tank. Where I used to work, we had an all fish exhibit that ran into the hundreds sometimes....and it was stocked well and had a huge over kill of a filter. Sea World (San Antonio) has several that run over the 10,000 ppm range.
In a reef, I've seen coral thrive at 15-20 ppm.