This is what mine looks like most of the time. At the time I took the picture the foam was only about 5 inches up the bottom tube, but you can see it was higher recently by all the foam hanging on the wall of the tube and in the collection cup.
ETSS skimmers spend a lot of their time looking like they are doing nothing, then build up foam for an hour or two, then go to absolutely nothing after a feeding. It's just the way they work. Like chew said, at night they tend to skim a lot since there's a long time between feedings.
Since the 800 has a very short main body tube, so you don't usually have the water/foam level up high in the tube like yours, especially if you use the Iwaki 55. My water level is in the box, only foam in the tube. If you do the air intake mod you can run the water level higher.