I also bought a new skimmer (Vertex In-280), and while it definitely pulled more skimmate, still wasn't making much of a difference with my nitrate problem.
Then I read about bio pellet reactors, so went out and bought a Vertex UF20 (just to the left of the skimmer). I also used MB7 to prevent cyano. I started out slowly with the bio pellets (as recommended), and initially didn't get much results, even after a few months. But gradually I increased the bio pellets and was able to fill the entire reactor with bio pellets (1000 ml). Then finally, my nitrates started to come down. It took another 6 months or so, but eventually they came down right to zero. I had to top up the reactor every few months. But no question in my mind, bio pellets do work, if you have a serious nitrate problem. Again, want to emphasize the importance of MB7 to out compete the cyano.
I still run the bio pellet reactor today, and my nitrates stay at zero. But interestingly, the bio pellet consumption has all but stopped, and have not had to replenish the reactor for almost a year now. I am even considering stopping it, just to see what would happen to my nitrates.
Once the nitrates were under control, I also added GFO to bring down my phosphates. That was with my 3 canister DIY reactor as shown earlier in this thread. It took another 6 months or so for the phosphates to come down (were over 1.0) to zero. But finally had my tank down to zero phosphates and nitrates.
And it really showed in the tank, with the detritus and algae pretty well gone completely. Of course, all along the way, I was scrubbing the rocks and vacuuming the sand. But eventually it all paid off.