As he says whenever there's space in the tank moisture,whether it's in the fuel or ambient air will condense on the surfaces of the tank.Cool the above and one gets ice.
This ice collects in the tank,and gels together..If you don't land in a suitable area(above zero)for a long enough time the Iceberg compounds.....
That is why Canada's principle airline(in the days of the 8')used to overnight the aircraft, to warm up the fuel in the Caribean,to eradicate estimated 500lb bergs...
