How bad is copper?
 

There's a store in town that's only 2 minutes from my house that has some cool SW fish and inverts, but I noticed on some of their tanks they wrote "copper Apr 20"... how bad would it be to buy a fish or two from them if they've treated their tanks with copper? I know copper can get into the silicone and then leach into the tank later on, so would it still be a concern even if they've done water changes? Their tanks aren't always great looking, but most of their fish look healthy. I have a reef tank with some mushrooms, zoas and LPS... if I net the fish after acclimation would this be enough to prevent copper from getting into my tank? Just curious...

As long as you don't put the bag water in your tank you will be fine......you should never add the bag water anyway

Wait till the LFS finishes the copper treatment on the fish you want to buy, then ask the LFS to transfer the fish to a non-copper tank and wait another week. make sure the fish eats before you pay. Copper can affect appetite of a fish.
oh yeah, don't put LFS water in your tank, regardless if you know it has copper or not. Many fish from different regions share the same water. You don't know what's in the water.