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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Ok starting to understand some things. Especially not to over react! Starting to set pH of water before watering (duh!) at one point my pH was 8.5! Got to normal then it crashed to just over 5. Got it back to 6.7 range… but adding nutes has me stumped. It seems natural to me to add them when the ppm500 scale reads less than 500 which it has for the last week! So ff nutes say to add every other watering, but thats not bringing it up. I don’t want to burn it or starve it but I’m out of tricks lol. Growth has slowed to a crawl at a time when it should be taking off! It is grand daddy purple fem. Sitting right at 9 weeks. Just before it is supposed to be able to flower. Soil grow indoors. 75 degrees 45 percent humidity. pH 6.7 mas a menos. Fox farms OF soil Using ff big bloom to treat apparent phosphorous/potassium deficiency . Also used ff grow big once. Always a bit less than suggested amounts .