Hydronic mushies, or more commonly known as mushies, is a nutritious foodstuff that is multi-colored and typically cube-shaped.
Mushies are instrumental in saving the lives of numerous crew members, including Boomer, Athena and Boxey, who are stranded in Galactica's rejuvenation center after a suicidal Cylon attack crippled the ship. Muffit, who had just recently been trained by Boxey to "sniff" out mushies, is employed to negotiate the convoluted maze of ventilation ducts, delivering lifemasks to the crew and rescuing a fallen firefighter from the flames (TOS: "Fire in Space").
In the 1978 writer's guide for the series, they are noted to be a "very tasty health food." [1]