Does he mean "yellow" by "gold" water? As Carol has said, it could be tannins, which are not dangerous, but which may bring the pH down ... and, actually, it's best if they don't bring that pH down TOO MUCH, lol. OR ... I think yellow water can also indicate that it's over-saturated with fish wastes, which definitely is not good! It's best when water is "crystal-clear" and has no color whatsoever ... unless one wants tannins in the water on purpose, to create a certain "mood".
P.S. Did your dad perform regular water changes when he had his tank(s)? If he didn't ... that's probably why he had "yellow/gold" water
