I haven't yet, though I plan to make some garum once the weather stays warm here in VA ( an unusually cool April it's been...)
The vat depicted is no five gallon
bucket. Images of nuoc mam....distilleries? ...fermenteries? ...factorys?... whatever they're called, show that these barrels are large - 100 gallons or more - and sit out in the open to be warmed by the sun. I wasn't able to find a smaller version. I do recall that a high school teacher who *ahem*... "toured" Vietnam...
described a fish sauce being made from an open-air mesh bag of fish with the drippings being collected underneath, rather than a fermentation vessel. I haven't seen anything to corroborate this account though. I've got to pick up the fish the next time I visit the ethnic grocery... I'll post an update, but will be using info from Christianne Muuser's page:
http://www.coquinaria.nl/english/recipes/garum.htm