"I don't think there is yet enough evidence that chlorella can treat and prevent B12 deficiency. A pubmed search turned up a whopping 4 results for 'chlorella B12'. No reputable vegan orgs or dietitians are recommending it either, so I wouldn't risk my long term health when I can just as easily, and much more cheaply, take a B12 supplement."
Wow, Hardcore IV--you are absolutely correct! Credit given where credit is due.
I'll explain why I made the comment: in Brendan Brazier's "Thrive" book he cites chlorella as a natural source of B12, which it is, and it should thus be consumed for this property (as well as a couple of others). However, after having read your post I checked another source, "Becoming Vegan" by Drs. Davis and Melina and they support your position with the following explanation:
"Some B12 reported in . . . algae and spirulina [chlorella is an algae] has been shown to be analog forms. These are somewhat similar to cobalamin but are not useable to meet human requirements, unlike real vitamin. These analog forms will not prevent B12 deficiency in humans. In fact, analog forms may even interfere with the action of real B12". (My emphasis)
I didn't know this and am so glad that you posted so I could check. You learn something new everyday: don't rely on a single source for important diet information.
Canadian chilling out in Japan for a couple of years.