After eating chlorella for over a year, and learning more and more about spirulina, I decided to combine the two. I started with the same amount I used for the chlorella, planning to alternate days. Mistake! Apparently spirulina is much more powerful than chlorella, and if one has not gotten used to it, one may have stomach distress and nausea. I cut back immediately, and read online about this, wishing that I had done so sooner. Things have calmed down now, and I hope for a long and healthful future with iHerb and Nutrex.