That's my preference to (Nitrate reactor). Although once you get to ZERO on nitrates AND solve the nutrient problem (assuming you can), you end up with a piece of equipment you don't need.
One reason I happen to like nitrate reactors is because they drop your nitrates slowly.
You can use just about any calcium reactor as a nitrate reactor, just don't use the CO2 stuff on it and fill it with different media.
Carlo