i believe my house is around 80 years old, give or take a few years. i know theres all old copper pluming in my house, and my fish have never seen ill effects.
i usually let the water run for 2-3 minutes before ill start filling a tank with it, in hopes of flushing any water that has been sitting in the pipes out already. this way, im thinking the water has no time to absorb any copper from any pipes in my house. with flushing and using PRIME, im hoping my way of thinking is right that no copper cna be transferred
ive been keeping fish for the better part of 20 years here. while most of that time was admittedly community, goldfish and cichlids, the last few years have been a huge aray of fish, some of which are/were very sensitive, and *knock on wood* never had a problem i could trace back to anything but avoidable human error for the most part