I took a gamble on some used dry rock in hopes that it wouldn't have copper. It has been curing in freshwater since March 5th. The water has been changed a few times and the most recent 100% water change was done 1.5-2 weeks ago. The water is measuring .03 ppm copper on the high range Hanna Checker. I have also tested the fresh water before the rock went in it and that is showing 0.00 ppm. When I first got the rock it went through a bleach bath for the first week, sat in fresh water for another week, dried for 3 days and has been in freshwater since. Am I putting my tank at a substantial risk with .03 ppm? Should I get rid of it and order new rock? The rock is 200 lbs in about 20 gallons of water and will be going into an established reef of 270 gallons. Thanks in advance for the advice.