I'm using 50% Pro Mix, 30% MG Organic Choice, and 20% my own mix. My mix was way too basic (PH 8.2), and way too rich. I'm not sure where I went wrong but it has bat guano, worm casings, kelp, blood meal, Greens Plus (human vitamin drink), bone meal, alfalfa, dolomite lime, molasses, a tiny amount of borax, sheep, cattle and chicken manure, perlite, vermiculite, peat, black earth... I thought I had all my bases covered. You should see the flow chart I did, based on every mix I read about. Well, it was a little over the top and the plants didn't like it. (And I won't mention the bills - the kelp alone was $35, then there was the shopping. Seven different places to buy ingredients just for the soil.)
My first grow was in my mix, pure, and it was going south in a bad way. Once I learned to check the PH on my own and found out it was PH 8.2, I knew I had to replant in something else. (I had the Agriculture Branch of the government test a sample originally and it came back 6.8. My tax dollars hard at work.) That's when I decided to go for something acidic and low nutrient.
Anyhow, I think that Pro Mix is good stuff to mix with MG Organic Choice. Both are inexpensive and readily available. And I am using up my mix and figure it must be good to have all that stuff in there, at least in minute amounts.
My first grow is one week into flower, and of the five females I started with, all are still alive and doing better. The soil PH is still quite high due to their growing so long in my special mix, and two have lasting issues but we are dealing with it. (crinkly yellow leaves...) Two are Gorgeous, and one is rolling along just fine.
My second grow in the 50% Pro Mix, 30% Organic Choice, 20% My Mix is looking very, very good. I mean, some look so leafy, green and tight that you wonder how they got all those leaves so fast.
I think the PH is far more important than some people realize, as is being very conservative with fertilzing.
