I recently treated my tank with Copper Power. I made a mistake of not realizing that this treatment was not ok for my snails. My tank has fish and snails only. All but 2 snails died. I did a 95% water change (took water down to the top of sand layer). Before I introduce new snails, I was going to check for residual copper. Should I get the HR or LR Hanna Copper Checker? Thanks for any help.