hi steve,
there is one other thing i thought of that is probably causing this debris to form inside the tank and lines, that is algie. Yes some diesel fuel depending on the quality will actually get algie that starts growing in the fuel and that will clog up the filters fairly quick.
There are additives that can be added to the fuel system in the tank that will help curb this problem, these can be found at just about any automotive parts store. A couple of treatments should be all it needs to get this stuff out of the system. You also may want to make sure your fuel supply source if it is a storage tank has a filter system on it so the fuel will be filtered when it it put into the truck if you have this.