Well would you like to test for 4-10 or so nutrients and dose precise amounts each time you need to dose?
Or would rather guess once or twice mid week and re set the tank with a water change weekly?
By doing this you can keep enough nutrients in the water without ever running out for more than a day or so.
No nutrient builds up too high since you do large frequent weekly water changes and nothing gets too low since you dose nutrients every 2-3 days.
The bottom line is that it maintains a relatively constant range of nutrients. Less unknowns and less dependence on test kits.
You can do it "naturally" with fish, no CO2 etc but the plants grow much better with CO2 etc. They also need more nutrients when using CO2 than can be supplied by fish waste etc.
Using inorganic nutrients, like KNO3, KH2PO4, K2SO4, trace iron mixes etc also you to control and dose pretty easily the needs of the plants.
These are cheap. Regular maintenace is the best thing for any aquarist keeping fish. Too many folks try and slack on water changes. I have not needed to use a medications nor lost a fish in 15 years. Very simple things like water changes do a world of good.
All the technology in the world cannot make up for basic mainteance.
See the "estimative index" on the DFW plant club site for more info.
Regards,
Tom Barr