Noob question, which PPM scale?

Good morning, afternoon or evening :wink: Some on here mentioned that I should not add nutes until the PPM gets at or below 1000ppm but now that I have a blue lab tester I’m noticing several parallel scales, so which is it that is being referred to? I have PPM 500 and 700 on my tester along with a couple others.
I’m at 100 for the 500 and 1200 (I think) on the 700.
Thanks !

You want to use 500 scale for most of your readings. A PH of 900 in veg and 1,100 to 1,200 in flower will work fine.


The scale used often depends on the scale used by the nutrient line.
Many of us use Jack’s 321 - Jack’s is user friendly and supplies info for all three major scales

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