I know that ph and ppm are two entirely seperate things...my GH ph test kit includes both ph down and ph up..so I can adjust the nutrient mix after Im done adding all the additives and such..I will adjust the ph to 5.8 since Im using coco coir hand watered....
Well maybe I am confused. When I was using a test kit the ph was determined by the color of the water. Your nutes don't affect the color?
That is the right ph for coco coir and your ppm for coco coir should be a little lower than it is for some other mediums, like rockwool, etc.
My real concern is the actaul beggining ppm of the water I will use..which is most likely city tap water..you stated its usually around 300..thats pretty high,and is likely to cause problems since Im a beginner...right?
The only way you would find this out is to use a meter that test's it. You would adjust for that beginning ppm, ie you want 1200ppm you would put your solution at 1500ppm, add for what was already there. The municipality that supplies your water has to be able to give you some idea of the quality of the water, contact them and ask em.
So I want to start with a water that has low ppm,so the end ppm of the nutrient mix is around 500-600..this will insure "safe"growing..with no unwanted salts and other metals in the mix....so should I use rain water or RO water...or should I just use my tap water?
Ok, you will not ever get a nute burn at that ppm, won't be giving them enough in coco-coir either. The only way you get unwnted metals and salts is if you add them. If you want to be assured none of those are there you should use ro water. This may be cost prohibitive for a small grow, mine was around $200.00. If you have city water it is probably fine, just let it sit for 24 hours before using it. Remember, people are drinking that water. I run 1200 to 1400 ppm for coco-coir. VV