I've been on a very long quest to achieve optimal results with my grows. I have taken on high-pressure misting aeroponics (see the endless thread in the Aeroponics section above). While this is producing incredible results, the real "gold" in the knowledge gained was finally being able to understand how to feed the plants properly.
Info relative to nutrients starts on page 28, and picks up again on page 34, with a link. Check out the thread, and then check out all of fatman's posts on ROI. I was directed there by an experienced aero grower who has been my mentor in this undertaking.
Fatman is a professor of botany some 30 years, now semi-retired. That he grows the magic plant and is kind enough to share his vast wealth of knowledge with the world is gift you cannot buy. I can save you some time and give you a short answer, but time spent reading that info will help you a lot. And likely save you a lot of money.
This stuff will sound complicated and confusing at first. I know. But if you hang in there, I think you'll see, as I did, it's actually very simple, and with the nute calculator linked below you'll find mixing your nutes painless.
The world of hydro nutes is filled with bullshit. That much I have learned. And (donning flame suit for the expected barrage) - Lucas had it backwards. And - you don't need any additives. All you need is GH Micro (mostly), Bloom, Cal Mag Plus (if you're using RO water) and maybe some Liquid Kool Bloom (not essential). I also use Epsom Salt, but again not essential. I've detailed a lot of what I've come up with in that aero thread. Also pics showing results.
MJ is a foliage plant. From fatman's info, tests done by the US govt in the 40s showed that hemp (MJs closest relative) grew best with an NPK ratio of 3-1-2. That is the golden number. Run 3-1-2 from seedling to late flower, then switch to 2-1-2 in final ripening. That's it. No magic additives or other horseshit.
I began following this regimen for several grows now. And the results speak for themselves. Fatman knows of what he speaks, and following his recommendations has produced the highest yields yet. I've realized a bigger improvement from feeding the plants correctly than anything else attempted to this point.
Now some strains like a little more mag, or less cal, or whatever. You may find you need to tweak your mix to suit. But beginning with the basic 3-1-2 formula will get you off to an excellent start. The plants will tell you if they are lacking something - adjust the mixture to suit.
