"I'm just as much in the dark as you are." Which is pretty much the truth there - even Bruce himself couldn't quite understand the nature of the magic that had contaminated the water, with as ancient as it was. Maybe if he had a better chance to study it he might have, but there was no way of doing that without attracting unwanted attention. No, his own curiosity wasn't worth that. "But I usually work under the assumption that if something can be done by magic, there's usually a way to undo it." So far, its worked out - more or less anyway, barring the rifts and all the other weird things that had happened in the last ten years since the Fifth Blight.