What you (or at least I) don't do for nitrates is add Prime or other chemicals.Been testing almost daily to see where my numbers are and everything checks out fine except nitrate. It is elevated just to the next color level on my API test chart. I've purchased the PRIME stuff that detoxifies the nitrate but it still is reading the same. Does it take a while for the reading to level off? Anything else to do for high Nitrate readings?
What you do for nitrates or anything else is to increase the consumers of nitrates or anything else.
In our tanks and in my opinion the best thing is fast growing plants. the plants will actually prefer to consume ammonia if present and therefore stop dangerous spikes when thing go wrong or in a new that that is cycling. And once bacteria get the ammonia, the plants will use nitrates for nitrogen. Plus consume phosphates and carbon dioxide and returning oxygen.
but that's just my .02