more important and in addition to h2o changes would be to run fresh activated carbon if it's a straight copper sulfate (such as aquarium systems sea cure), or poly bio marine's poly filter if it was a chelated form (such as mardel's coppersafe or seachem's cupramine ...), copper gets absorbed into the substrate, continue filtering with the above even after levels test low. best to remove it if it's not already to late.