not knowing the polymer you bioballs are made of I can only go out on a limb. But yes IMO bio balls can definatly absorb serious amounts of copper, then it will leach them back out so chances are you'll go from LOW reading to the level your shooting for to serious OD. you should not be dosing copper with any signifigant amounts of media, including but not limited to live rock, sand, silicone, polyfiber, acrylic, ceartain types of carbon, any plastics, all mentioned can absorb and re-release copper. except carbon attaches through adsorption not absorption but you get what I mean.