The best plants for reduction of nitrate are ones that grow quickly and easily. Hornwart, anacharis, hygrophilia (make sure it's not a noxious weed in your state!), water sprite, etc. Many propagate by clippings, which means you can make more of them reasonably easily.
Duckweed is a terrific nitrate sponge, but it can be a real nuisance.
Also, if you have no other animals in the house, you can put pothos into your tank. Just the roots. Dangle them in there and let them grow. These are also very good nitrate sponges. But pothos is poisonous to plants, so if you have a cat that likes to eat your plants, don't use the pothos method.