The quickest way to fatten up is live black worms, followed by frozen blood worms, followed by cut shrimp.
Quickest way is not always the healthiest way. After the fish is acclimated to the environment and strong, switch to your favorite food. New Life Spectrum is popular, massivores is also popular. I always NLS, after they finish, add cut shrimp.
is it better to fatten them up? because all of my plecos look healthy, not skinny, not fat, ive seen people fatten them up before, but what is the benefit??