Just a note, legbamel started this posting, I was just trying to offer how mine has worked. Aquarium salt has worked for me, added per the recommendations I'd found online to create a decent "brackish" mix. I finally moved the last of the guppies out of there this Saturday when I was cleaning. They went back into the "general population" 55... Seemed fine this morning, but I'll be watching them for the next few days in case of shock.