Check out this thread. It might give you the answer you looking for. Depending on the size of the tank and how much work you might want to put into it you might consider waiting for the next Petco dollar per gallon sale.
Neither glass nor silicone adsorb copper. I've used copper treated tanks countless times for inverts. Clean it well, ideally with bleach, and you'll be fine.
Sorry to jump on this post, I have a related question - can equipment like powerheads and Ato floats that were used in a copper QT, then be used on a tank with corals if they have been cleaned well enough? Citric acid / bleach / Milton tabs etc?
thanks, I just got a cheep bucked from home depot. I just need an ato for my nano tank while on vacation. Thought I would use a small used qt tank for it 5 gallons since i upgraded my qt to 10 gallons.