We occasionally clean cooling towers, which involves using a pressure washer (carefully) on the delicate tower media. Often we have to choose between either obliterating the media or removing all of the buildup (we choose to just leave extra stubborn buildup). I've heard of people using wire brushes (urban legend?) to remove this stuff, but in reality we aren't ever given enough time for that. I'm curious as to how all of you handle this? Special chemicals?