Join Date: May 2011
Location: Elk Grove, California
Caused by gas saturation in water and is "amalgous to the 'bends' in human divers." It is mainly nitrogen gas that is toxic to fish above 104% saturation. "This condition may arise when cool and gas-rich water is quickly warmed." Basically, cool water heated by a heater. It also happens when "newly set up aquaria have been filled with cold tap water and quickly warmed to operating temperatures." Such as when we draw lukewarm water from our tap.
Source, A-Z of Tropical Fish Diseases and Health Problems by Burgess, Bailey, and Exell.