From the dark side:

When fish die, most of them do not float they sink to the bottom. From my experience this is particularly true for the larger fish. A few after laying on the bottom for a number of days decay produce enough gas that they will finally float to the surface. You may have lost may more than you think.
A number of weeks after a cold spell & a cold water inversion my large tilapia began floating to the surface for a two week period. Those that did not surface were turtle or gator chow, never to be seen.


SWAQ:: Stress from warm water & low oxygen. My pond is now 90 degrees.