Do you have to change your res?

I was just wondering if you had to change your res out if you have a ppm meter and ph and keep ur temps regulated. Is it a must or at your own discretion. Only adding nutes when your ppm drops.

this is debatable. i say always flush hydro, never soil. but my own experience, you might find it differently for you. this is all of course talking about personal smoke, not commercial.

Realize that plants better take up different nutrients at varying pH levels and then only what they need or prefer. That's why it's not a bad thing for pH to slowly fluctuate between 5.5 and 6.2. Also you never know what is making up your PPM after several days of your plants eating and drinking. For all you know they are chowing down on one nute while lightly snacking on the others, eventually it get's whacked out. That's why it's always a good idea to do a complete water change every 7 to 10 days so you can get back to proper proportions.