I cycled my first tank with a shrimp from the seafood counter. It worked, but it stunk and the fuzz that grew on that was so gross. Next tank, I cycled with flake food, I put a large amount into a piece of thin cloth, I think it was pantyhose or old cotton bandanna. Twisted and tied it shut, let that just sit in there. It still got kind of gross looking, but was easy to remove most of it in the cloth wad, and siphon out the rest when cycle was done. That should keep the cycle going while you're gone, a nice big wad of food flake.