Have you tested for copper??? If so,and your test is posative,even water changes may not remove all of it.But I would do as much(up to 100% if needed)as soon as possible.Plus try looking for a poly sponge at your LFS.Some of these sponges do claim to remove copper.Any filter pads you are using will also need to be replaced...You should also move your corals and inverts to another tank as soon as you can.The copper will kill them before you can clear the tank...Once the water change is done,wait a day and retest.If copper is still present you should do anoy=ther water change.Then if it's still there you may need to pull out the substrtae and rock.You see copper will saturate into rock and substrate and slowly leech it back into the water...I wish you the best of luck,but be prepared to start over if it has gotten into the rock and substrate...