Not true lizardbreath. I designed complete building automation, refrigeration, and heating and AC systems for years. It will help and will also help your home meet the 10% fresh air exchange code, which will help your family avoid the sick syndrome.
Although here will be heat loss along the tube, how much depends on length, tube size, insulating factors, rate of travel of the air (fps), and both indoor and outdoor temp. It won't heat the pond, but will help prevent freezing over from occuring. The same heat loss you are worried about happening before the pond will be happening in the the pond. It can also help take the edge off the heating bill for those who heat.