Kole, no matter that window is open. If you have HCl even small amount in garage it will rust anything which is made of metal. It will not happen overnight but it will happen. I lost few sets of tools and I was just mixing Stannous chloride from time to time. Wits AP process in garage rusting out everything made of metal is not "if", but "when" and it will be sooner than you think.
Your water bottle cant be hermetically sealed because whatever aquarium pump push in must go out. The best suggestion was to make one pipe go out of water bottle to the window outside. But I cant see why cant you just keep bucket with AP outside. Be advised that dissolving pins in AP will take weeks if not months depend on volume. It will take you well in to the spring so there really is no need to ruin your tools and garage over few $ worth of gold from one bottle of acid. Wait till it will be warmer and leave your bucket outside.
