I have a 40gal QT w/ a hippo tang and yellow tang in it. I am treating the tangs w/ Cupramine b/c about 2days after i got them they started rubbing on the pvc pipe in the tank. I followed the directions on the back for the correct dossage, but when I use my copper test kit, it is not reading and copper in the water. Has anyone else used this product, and have you had the same problem, or could it jsut be that there isn't enough Cupramine in the water, or the copper test kit doesn't read the Cupramine in the water. Any help would be greatly appreciated in this case, so I won't cause any harm to my new additions.