"Joel M. Baldwin" wrote:
Logical and reassuring, however I would have expected that a large portion
of that 60watts to be expressed as mechanical energy in the water movment,
not as thermal energy into the water.

Most of the power *does* initially get used to move the water. However, the
same effects that result in the water movement being damped in the aquarium
(friction, etc.) ultimately result in most of the energy being converted to
randomized heat.