Using HANNA Nitrate LR checker:
Based on video instructions on youtube,
My own dilution method: Original sample with lots of tap water dilution,
1.93ppm
With DSR EZ Carbon (more than a capful): 1.25ppm
With Cobalt Total Nitrate resin instead (210g): 0.06ppm
Conclusion: I don't think the DSR EZ Carbon is as great as the online forum community puts out to be. Perhaps they were comparing reef tank to reef tank and not marine fish tank (20+ ppm is ok) to reef tank (not more than 5ppm).
So Cobalt Total Nitrate it is. I need lots of this. It is also able to recharge/reuse.