deep six is evil, evil I tell you!
just recalibrate your hydrometer so it matches that of your lfs refractometer. For example mine reads .005 high so to make up water at 1.025 I need to have my hydrometer read 1.020.
That's what I did. But I got rid of the evil, evil deep six. Stupid thing. I thought it was better than what I had, I did a water change, my sg was all off, I screwed up the whole tank and lost my brittle star...
my cheapo swing arm thingie is better, and wasn't off as much as the deep six, however, I'm getting a refratormeter as soon as I get the money.