PPM differences in Colloidal Silver

Hello,
I've been making some CS with my SilverPuppy and seem to get a lot of sludge (which I filter out). Also, is does seem to tast a bit bitter but I thought that was normal. I had brewed up some to 20 ppm to see how it may compare to some Mesosilver I had purchased in the past. Meso is much darker but tastes better. Also, my meter measures my brew to 20 ppm but the Meso, which is advertised to be 20 ppm, measured at 10 ppm. Why the difference? Any ideas on how to brew with less bitter taste?
Thank you,
JLA Tweet