Good topic Tinytoon!
Many of the plant problems I've seen asked about here, are at least partial PH problems; that appear as certian nutrient deficency or lock out problems.

I am a firm believer in the phrase "when all else fails...read the instructions".
See what the mfg of your stuff has to say about recomendations both ppm and ph.

In my personnel grow, using rockwool w/Dutch Masters' Gold, I find best results 5.3-5.5 and is close to mfg suggestion of 5.5. In another grow using Pro-Mix I use what the local greenhouse operator's use ph of 6 +/- .2 and never had a problem using DM Advance in that grow. (DM recommends 5.8-6.5 btw).

As LOC NOR points out tho, it can be strain dependent. It is not unusual to find you need to go a little lower or higher to make certian plants happiest.

Bigtopfinn,
That chart is excellent to give people an idea about what nutes may or not be available at differant PH's. (I saw that chart just last week on another board, while talking about Pro-mix and PH) Pro-mix seems to fall between hydo and soil for PH use.
The chart also gives you an idea why you can use less nutrients if you hit the PH correctly.

I am curious why more hobbyists and small indoor container growers don't use pro-mix since it is so inexpensive and very forgiving to grow in.
oldmac Reviewed by oldmac on . yet another PH post So I visit this site pretty much everyday reading this and reading that, trying to absorb as much info as possible. So I was looking at the FAQ section of cannabis.com (not the one on the message board area) and to my surprize I read that the optimum PH for Hydro is 5.2 and not 6.0, actually the PH range stated best to be in is like 5.1 to 5.9. anyone want to jump on board the discussion train about this? also states that you can lower your ppm by using this range since plants can more easily Rating: 5