I would go with arbico organics @Cerebral Goo and while ordering them order a big ass batch of predator mites (hypoaspis miles) as they will eat up fungus gnat and other invader pests eggs and larvae!
Only seen a couple of little grey lookin bugs that came in the soil. Haven't added anything else from outside yet though. I haven't had one fungus gnat in two years of coco! Knock on wood!!!!!!!!!!!!!!!!!!!!!
Will check the Arbico. I've seen it, but never checked it out. My computer to do list is gettin hefty!