Mixed bag. Copper can get into the silicone on the tank and as far as I know there is no way to clean that out. Should you get the tank clean the tank with a mixture of either muratic acid and water (1 gallon acid / 100 gallons water) or citric acid (1 1/2 pounds citric per 100 gallons water) thenrinse tank throughy with fresh water. Fill it and let it run for a couple days and then test for copper. If its a good deeal replacing silicone isnt that hard.
What scares me is that some of the people I have contacted seemed like they bought the whole fish tank kit IE, filter lights , ect and didnt know why I was asking about copper. They all say "no" no copper,but who knows.
Just make sure if you decide to replace the silicone you get one for aquarium use.
There is chemicals in the regular stuff to prevent mold problems from what I am told and the chemicals will leach out into the system and kill off fish and/or inverts.
There is a copper test you can buy for under $12.00 if memory serves me correctly.
Denise M.