Curious about this stuff too, but couldn't remember where I read a couple of negative comments in an RC thread or two. Randy H-F has some concerns but doesn't seem to give it the thumbs-up OR down...
http://www.advancedaquarist.com/issu...y2002/chem.htm
He seems to question the usefulness of slurries in general.
But here you guys have logged two stellar reports, so...
