Kelp-Milk is a kind of milk that is sold in Bikini Bottom. It was seen in SpongeBob's fridge, if you look closely in the episode, Procrastination. It is possible that it could be also a type of Kelp Cream. It is also possible that others buy it. It is unknown if it will ever appear again.
Kelp Milk is appears to be a small carton of milk that is white and pink in color. The text is also written in red.