Ive been watching greenhouseseeds videos on youtube. Really amazing.12 foot indoor plants yielding 3000 grams per plant. Anyways, on every plant they tell the ph being used then after that they give a number like 1.5 to 1.8. I cannot understand what they are saying. I don't know what they're referring to. Can anyone explain this to me?

like its o-10.

and theyre ph is extremly acidic. your water levels are suppose to be 6-6.5 for most plants and that is nuetral

They are not talking about the PH they are referring to EC or TDS also Known in PPM, it is an amount of total disolved solids in the nutrient solution they are using.

ah that makes more sense. they were talking about the thickness of the stem and large root system and that it can handle more nutes. Does anyone else flush the plants once a week as they do? I respect your opinon cali-hi, but for one, look at those plants - wow. how could they be wrong? and two - rain (of course not acid rain) has a ph of 5.6 so their ph of 5.5 seems natural to me. thanks for the info though.

The ph of the rain water all depends on where you are at. Also, what events (like volcanic eruptions and such) have taken place in the world... the wind currents, etc. But most of all if you average out your ph... it could be over 1 point different than an area 1000 miles away.

Cali just missed what he was talking about with the 1.5 and 1.8. They refer to an ec of 1.5 to 1.8. Electrical Conductivity, Total Dissolved Solids, and Parts Per Million are all measurments of the amount of nutrients in the water.
There is difference in the ph you use, determined by the medium you are using to grow in. And rain ph can vary depending on the pollution it passes thru on its way down. Hope you got your question answered. VV

Yes it does, I learned there is an ec meter. Saw one on ebay. Cool.