Just a heads up - Prime doesn't fix nitrate, it temporarily binds it for around 24 to 36 hours. It does the same for ammonia and nitrite, it temporarily binds them. Assuming the source water nitrate is lower than tank nitrate, the way to lower nitrate is by doing water changes. Or have live plants in the tank as plants take up ammonia as fertiliser so there's less for the bacteria to turn into nitrate.