Where you get your Spirulina is a big deal. Due to Spirulina’s ability to pick up and absorb toxins from its surroundings, the environment in which it is grown is very important. It is necessary to make sure the spirulina you get is from a clean and reputable source.
I have been experimenting with different spirulina products for years now and the Hawaiian Spirulina by Nutrex still ranks #1 on my list. They are heavily regulated and ensure only the best quality Spirulina. Not only that, but their Spirulina also seems to have a less harsh taste (if you buy the power. You cannot taste the tablets).
The cheapest place to buy is at Amazon.com