Tube to floor drain stops working and bucket in unit fills up

My dehumidifier has a hose that drains into a floor drain. After some time, it stops draining thru the tube and instead, the water container in the unit fills up with water. What causes this to happen, and how can I fix it. I've cleaned out the tube, as their is a film or mildew(?) that may prevent the water from going through the tube. The tube runs about 10 ft. to the drain. Anything else I can do to make this drain through the tube to the floor drain?