I think the ULNS approach also works (0 NO3, 0 PO4), it does work in the ocean afterall, it's just that people tend to pull only some of the building bricks from either method, and expect results from it. It's a bit more to it than just bottoming out nitrates and phosphates. Maybe that is why people are not seeing the promised results with it. Pretty much the same goes for higher nutrients, there are more to the equation than just these two blocks.