I second this. Keep it simple. They make an all purpose 20-20-20 which is an often overlooked choice among growers because it's not sold at hydro stores, it's sold where the real gardeners shop; nursery's.
Like many, I started out as an outdoor grower. Realizing that indoor cultivation was a bit different, I went to the now defunct Cannabis World (really dating myself here) and started looking around. Keep in mind that CW was the equivalent of IC, so you can imagine how intimidating it was seeing bud on top of bud...everywhere. Of course, I was reading everything I could find, too. After the initial shock of CW grows wore off, it became clear that many of these astonishingly successful growers did not do things as explained in the growbooks - that was before I understood that many growbook authors did not actually grow weed - and that quite a large number used Jack's Classic fertilizers. So, I started out with Jack's, too. I've tried other fertilizers, all canna-specifc, and always went back to Jack's. At this point I use JC exclusively: All-Purpose in veg and Blossom Booster in flower. Pro-Mix right out of the bag and Jack's. Nothing else added. Nothing. Folks can see examples of plants grown with Jack's in a thread link'd in my sig.
This isn't to say that it's the "best" fertilizer, if such a thing even exists, or that it's better than whatever else. I've grown great plants with PBP, GH, and FN, too. For me, Jack's is far easier to use and more foolproof. Like totally. It also doesn't hurt that its cost is small enough not to figure into one's expense budget.
Simon
