Ah yeah, as a challenge to be sure the cycle is complete. Yeah, feed the tank at least a week with food (coould be any, really) as if you had fish in it. If you see no change in ammonia or nitrite, the tank is cycled.
As for the nitrates, I still say that you will miss the joy of the hobby if you live by the numbers. Nitrate, IMO, is nothing to be scared of. It is something to track to see how your tank is doing...are you over feeding, over stocked, not doing water changes...a road sign for you. Not something that will kill the tank tomorrow.
I've worked with systems that have nitrate levels over 200ppm with no issues