I always keep my 100L diesel fuel tank full - except for the past 12 months on the hard stand when it has been nearly empty.
The fuel I drained today from the Raycor filter drain point and the fuel I drain from the fuel tank sump drain appear perfectly clear with no sediment. I did, however, notice a slight red tinge to the fuel I drained from the filter but again no sediment.
I'm concluding that I have no condensation in the tank, no "diesel bug" and intend to re fill the tank.

But first a couple of questions for diesel mechanics or other knowledgeable persons :
(1) what colour and texture is the "diesel bug" ?
(2) I rinsed the filter in petrol then methylated spirits. No sediment or other muck appeared so the filter seems fine. Is it acceptable practice for me to re use the filter (just in case the re fill process creates a problem so I won't wreck a new filter) ?
(3) the centrifugal disc in the Raycor filter has not moved since it was installed. I've always assumed this was because the filter was just too big for the 3 cylinder 27hp Yanmar engine and so I did not view this as a problem. It this a reasonable conclusion?

(By the way.... although on the hardstand I always run the engine for 15 minutes every couple of months. It will be on the hardstand for another 12 months).