Nuts! Ages ago someone planted a black walnut tree on the property line way back there, or some squirrel helped increase the tree diversity by one species, but now it's there so you deal with it. In general it's not such a big problem that it requires any action on our part, just don't plant any tomatoes close by. Now this brings me to a current problem: the flow of the cascade into the lily-lotus pond was diminished and it remained so even after the massive filters were flushed out. So the problem must be at the intake end of things. One intake is in 4.5 feet of water, so the Phactor began by examining the accessible intake at the overflow gate. Both a net and a bottle-brush filter keep crap from getting to the intake, but somehow an immature black walnut had found its way in and it would get sucked up into the intake without totally blocking it. You find all of this out by frogging around in the bottom of a pump box with your hand not quite knowing what you will find. And that was all there was to it. Remove walnut, plug pump back in, cascade flow restored. Good thing that walnuts do not regularly fall into the pond and make their way past the pump defenses. Good thing it was just a pond pump and not the intake to a jet engine or nuclear reactor. Good thing walnut removal is within the Phactor's technical abilities.