squishie is leading you correctly ezmac. you will want to remove the sand for all the reasons mentioned. you can do the same with the structure depending on it's porosity. you don't want to use items that can absorb the medication and cause levels to fluctuate.
what copper are you using?
you need to purchase a test kit of the same manufacturer that makes whatever copper you are using (i.e. seachem cupramine and the seachem multitest test kit)
you should be testing level once if not twice a day and making trips to your LFS is cumbersome and not practical and you have no way to assure the test is being done correctly or with the correct test kit.
get an ammonia badge alert as a backup.
testing ammonia with typical test kits while treating with most copper medicines will yield incorrect results.
take note of your fish's normal behavior for activity, respiration, feeding, etc and you'll notice when water changes are due. typically every day to every two to three days is not unheard of but will change based on how much you feed and what biological filtration you are able to sustain during treatment.
you need to provide pvc structures or fittings for the fish to hide and feel secure. a stressed out fish is no good. pvc does not absorb medication as easily as rock or other porous decorations and is easily sterilized for reuse.
i would not move him from qt rather slowly begin to stabilize and improve water quality over the course of a day.
do you have a HOB or power head providing agitation of the surface for oxygenation of the water column? the air bubbler is not a bad one but you do not want to use an airstone with too fine of bubbles as it will just act as a protein skimmer leaving residue on your glass and slowly removing your medications.
let us know how it goes and hope this helps. there are tons of worthwhile threads and information stickies on here and RC to read over prior to your next fish addition in qt as well. be sure to take the time to be diligent about this and your next effort for optimal success. g'luck!
