The best answer I can come up with from a quck google search is put a small piece of raw fish in each tank and leave it until you get back. Next question...
Nitrites are finally 0 within 24 hours of dosing 3-4ppm ammonia.
Next question. I have to go out of town for work for 3-4 days. Will not dosing the tanks with ammonia for a few days mess up the cycle? I don't want to put fish or shrimp in until i get back. (and get someone to feed multiple tanks while i'm away)