If you take a Rx antifungal and the tongue clear, it is a fungal infection, but if you use Grapefruit-Seed-Extract and the tongue clear, you can not be sure the problem is candida since Grapefruit-Seed-Extract is an antifugal but a bactericidal at the same time. An Hydrogen Breath Test is the right test to detect SIBO. I also have friendly flora according to my CDSA, but I am sure I have candida. My CDSA also didn't show yeast. When candida penetrate the intestinal ephitelium (cells)is because it mutated to its mycelial form and became intracellular. This invasive form of candida isn't "floating" in the intestines. So, there is almost no chance to show up in stool test. Less, when you have been following an anticandida treatment for some time.