I don't know how Algin will affect leaky gut, but Algin is not known to mobilize mercury. It's very absorbant and has an affinity for heavy metals. If you ever open a capsule and put it in water you will see that it becomes like a thick, slimy sponge.

Algin is different than any other seaweed product because it is a non-digestible fiber that remains on the colon and absorbs heavy metals to prevent reabsorbtion. Chlorella, for example, actually chelates mercury and will mobilize it. I use Algin and chlorella together. In fact, I take Algin with any chelator I take.

I assume Algin would be beneficial for candida for the mere fact that if blood-mercury is lower (which algin will help facilitate), then the immune system will be stronger, which in turn will lower candida issues. In fact, I've heard this kind of feedback from people who've used it.

Hope this helps.