As long as water is moving, it will not freeze.  Our Freeze Valve is infinitely adjustable from a full steam to a pinpoint stream or off for summer.  It can be adjusted to deliver as little as 2 gallons in 3 hours.  If your trough is of reasonable size, the additional water at night when few animals drink will not overflow the trough.  The arm on our Weight Valves are hinged so it pushes the valve open when the water level goes down.  Because the freeze valve will deliver water at night (when no animals are drinking) the weight floats up, but will put no pressure on the valve.  This is unlike a float valve, because any water added to the tank (and not drank by animals) will submerge the float and bend the float arm, potentially destroying the float valve.