What does crayfish eat?

i have a crayfish pet. i bought it at the supermarket. i thought it would die in my freshwater tank, but i guess not. i think my tank is dirty enough to support saltwater fish. or as you guys called it, a matured tank? anyways, i dont have any food, but fish pellets. it actually eats fish pellets! i didnt know that. my crayfish eats fish pellets for some reason. now, how do i submerge fish food pellets so that my crayfish can eat it?