Thx,im sure youre approach isnt much different than mine except maybe the soil depending on what ur using. Im using coast of maine bar harbor blend organic soil. Im using well water like you & GH nutrients. Im going to try & do like you said. As far as the ppm after what I read & what aquaman said if I do get a TDS meter itll just be to get a general idea of things but I wanna keep it simple. I havent tested my water yet but ive had lots of well water over the yrs & mine tastes great so hopefully its in neutral range. But if I understand you correctly I check the pH of my water then add my nutes & check again & add my pH up or down to get optimal lvl. Then check pH of run off & adjust accordingly?
My soil is 50% potting soil with no additives, 30% cocca, 14% vermiculite (course A3) and 8% perlite. I feed the plants with Mega Crop and Sweet Candy as well as weekly I add RAW NPK nutes to the food. For the medium, I feed it with Recharge weekly. Been using this menu for a number of yrs with great success.
Once I get the mixture put together and lastly check the ph which usually is higher then before I added the food. The ph is around 6.3 before adding the food, then it raises to around 6.8 - 7.0, that's when I add a very small amount of pH down to the mixture and shoot for around 6.0.
I then check the EC and verify it's roughly close to the desired target. When all is well I add the mixture to the soil and collect runoff to compare the EC and pH against the amount that went into the soil.
For example, if my plants are about 11 weeks old and late into vegetable state, the desired EC is 1.3 (ppm is 660) and of course the pH is hopefully 6.0.
If the EC reading on the runoff is somewhere in the desired range, the plants are eating everything I'm giving her, If the runoff is higher (say over 1.4) then I'm feeding too much and if the runoff reads lower, I'm not feeding enough.
Same with the pH, as long as it is within the 5.8 and 6.5 the plants are OK with that. If the pH reads around 7, its time to flush and pick-up where you left off.
As a warning - The above stats works for me and may not work for everyone. I live in the deep south and we have a lot of sun as well as rain.
Good luck