I tried that additive but by then it was too late. I recently discovered that so far this year 6 of us Kubota owners in a small town have run into this. There's only 3 diesel dealers in town; 1 sells off road.
I have twice had to have the tank in my BX23s removed and cleaned. Has anybody designed an access plate (similar to an oil pan on a car) to allow drainage and cleaning without removing the tank?