I have noticed my nitrate levels haven't dropped to zero and I have had the package for 10 days now. My earlier readings indicate it has cycled but nitrates still remain around 15 ppm or so. This is even after daily water changes. I am using RO water and have a wet/dry without any bioballs in it. Should I get my levels down to zero before asking for the second shipment? Do you think my nitrates will eventually come down to zero? Thanks