It's unlikely to be Hg as it wouldn't float. Even the highest excretions of Hg would be undetectable by sight. Why don't you do a 24 hour urine test and send it to a lab and see if anything's coming out, only then you will know if it is a Hg chelator or not. Chlorella is a mild chelator but is none specific, rather like a shotgun, mobilizes Hg all over the place. Not a good Idea if you really think you have allot of Hg.