Thanks all for quick feedback.
This species tank is setup with Rotala Macrandra in mind. And I have homemade soil subtrate covered with river sand.
1. Water change - should be minimal to avoid pH shock + to maintain dissolved CO2. My habit is to change water once a week.
2. Fast growing plant - not possible, this is hairgrass + r. macrandra ONLY tank.
3. NO3 is a fertilizer, why keep it low ? - yes, but red plant needs low NO3.
4. Chemical - expensive and might change other water parameter which is undesired.
5. Zeolite - cheap, reusable, won't affect KH, non-toxic, no maintenance.