cycle a new tank

Hi guys,

I am new to salt water so bear with me here...

I have set up a 20G fish only. Started with live rocks and live sand. There is no fish in the tank as of today. I have been adding a bit of brine shrimp or fish food every other day to keep the bacteria alive. It has been 8 days and all my readings are still zero. Shouldn't I get at least a bit of ammonia? how do I kick start the cycle of the fish food won't do it?

Thanks for your help,