u/Revenoon

I understand this is probably dumb but I was wondering if there's a way to make safe sashimi in a commercial freezer. The FDA says to Freeze Fish below -20C for over 7 days, but most commercial freezers go from -18 to -23C. Salted Ice reaches -20C, So could I use that or another substitute to eek out those 2 degrees? I understand I could probably risk farm raised fish at home, but I was just curious.