I've been prophylactically treating two hospital tanks with cupramine for 28 days, yesterday was the second to last day and the level in one of the tanks dipped below .5, maybe .475 (its so hard to tell with those test kits, I had my wife help). Anyway other than this one day its always tested .5 or a hair above. So what if anything do I need to do; start over, give it a few extra days, etc... Any thoughts would be welcome.