cycling a new tank?

[Skimmer Juice]

I just set up a 125g tank and iwas wondering what the amonia level had to be at before you should do your first water change.The tank has been running for a week, now I used filter media from my existing coral tank ,quit a bit, all ro water, and I used cycle the amonia reads today 20 the second color down on the chart.So iwas just wondering if I had to wait longer to do the first water change.I also have my sump filled with live rock and a bed of A.R.M Argonite reactor media I belive