I keep two types of fish sauce at home: 3 Crabs and a brand of Thai fish sauce.
I use 3 Crabs fish sauce for Korean and Vietnamese cooking. This is because most of the Korean and Vietnamese cooks I know love 3 Crabs fish sauce the most. The reason why I keep a separate Thai fish sauce will be explained in a post about Thai fish sauce later. 3 Crabs fish sauce is made in Thailand and Vietnam, and blended in Hong Kong by Viet Huong Fish Sauce Company. They also make other brands of fish sauce, but 3 Crabs is the standard one. Fish sauce is necessary for all Vietnamese cooking, and is necessary for kimchi and Korean soups (although in soups, you can use Joseon soy sauce instead). 3 Crabs fish sauce is easy to find at any Asian grocery store.
I used some of it already; the fish sauce is not clear colored 🙂
Korean (액젓 – aekjeot – ayk juht)
Vietnamese (nước mắm – nook mahm*)
Chinese（鱼露 – yü lu – yee loo – “fish dew”）
*I cannot pronounce Vietnamese correctly so the pronunciation may not be the best.