Hi David,
Sorry, not going to be of much help to you here, I have used the Sera Products before, but not the Nitrate Test Kit, Nitrates should be kept around 40 or lower if possible I think it is, So more water changes and more frequently, You may also want to test the Nitrate Level of the water that you are putting back into the tank, as this can also be High in Nitrates, Not sure why you have to use boiled filtered water with this test, Hmmm, I'm abit confused there. :-? :-? :-?
Maybe wait and see if some-one else here has used the Sera Nitrate Test Kit, and see what there advise is, I think alot of people use the Aquarium Pharmaceuticals Freshwater Test Kit.
Anywayz Good Luck and hope you get it sorted. :bounce: :bounce:
Lynda