You can use anything that decomps...I say to avoid flake and pellet food as it will swamp your system with phosphates. This of course is why I say an uncooked shrimp normally. If this isn't something available to you you can simply use pure ammonia to dose the tank up to 2 ppm
to start the cycle. As you test the ammonia, nitrite, and nitrate levels you will know to dose back up to 2 ppm
until all ammonia and nitrite are consumed in a 24 hour period to know you can safely add livestock to your tank.