If you have live rock and sand you may still have some copper in the system. These items are like sponges for copper. Any med should be used in a qt
setting. To much damage can/will be done to a display tank with meds like that.
Keep doing water changes and hope for the best, but you may have an invert problem for a while..sorry to say. :|
I would also run GAG for a good while to help remove any traces.