Yellow Prussiate of Soda - Aquarium safe?

[Deep Seven]

My source of potassium chloride, has a tiny amount of Sodium Ferrocyanide Decahydrate, "commonly known" as yellow prussiate of soda.

Anyone know if this would harm my fish? I'm not going to be using very much potassium chloride, so the amount prussiate of soda will be very small indeed, and will be mostly buried in the substrate.

 

[jsoong]

This is controversial & everything I read were conjectures.

YPS is used as anti-caking agent in table salt. For years the standard advice is to avoid table salt (due to the cyanide in YPS). I have also read *opinions* that said table salt is fine and YPS is in such low concentration that it had never caused problems.

Cyanide is naturally occurring, and people & animals can metabolize it, so a low level is fine. (That's why you get it in table salt!). Now, I have not read anything about the lethal (or harmful) concentrations of YPS in fish. (In people, LD50 is ~100 ppm of HCN.) I don't know how much free cyanide will dissociate from the Ferrocyanide, but it would be a magnitude lower than HCN.

So, I tend to agree with those who said salt with YPS is OK in fish tank (since the conc will be much lower than 100 ppm), but realizing that this is not backed up with any studies!