Alk and nitrate cycle question?

[SaracensRugby]

So I have a newer 315 gallon display setup (less than 12 months old, 400+ total water volume), and my nitrates are bottomed out at zero with Nyos tests. PO4 was at .2 with hannah checker. I have about 10 SPS small frags, that were introduced in the last month and are starting to show signs of growth. I have chaeto and another plant I got from ISPS in my 50 gallon refugium that is growing like weeds. I have not started dosing alk/calc to this point, but my alk is increasing from 8.5 to 9.1 per my trident. The rise in alk started as I started dosing small amounts of nitrate (loudwolf), in an attempt to get nitrates to around 5. Nitrates remain at 0, even with small dosing (probably need to dose more) But I have read that the nitrification cycle could add alk back into the tank. Did I understand this incorrectly re: nitrate being used up by the refugium?

So, how do I increase nitrates and then stabilize them, so it is not impacting alkalinity? Just turn off the lighting period in the refugium, or greatly reduce it to a few hours a day? I have about 10 fish in the display currently, with another 4 being added in a week once they are out of QT.

Thanks in advance.

 

[Jekyl]

Smaller amounts of chaeto. The larger the ball, the more nitrate removed.