Months ago, I filled up with bad diesel and ended up with a nasty problem in the system.
After changing the front diesel filter several times, things only improved briefly. So yesterday I decided to take drastic measures. I removed the tank and cleaned the intake strainer.
I washed out the tank and then put the system back into operation using an antibacterial agent.
lifting up for drainig the tank completely

Run your finger briefly through your filler neck. *puke*

nasty

No more cleanig for tho filter... completely clogged. rock solid back mass.
Ordered two new.
But i think i found out why i struggeling with this for mounth!
Algae can easily multiply in diesel, and especially in biodiesel. This is particularly true when exposed to air (diesel is hygroscopic and therefore attracts water).
The canisters I used to refuel with after replacing the filters were also full of this black slime because I had gotten into the habit of leaving them open when empty. But diesel doesn't evaporate like gasoline. It stays in there and you end up with an algae brothel.
And the HMMWV's tank was also almost completely empty after the hot summer and already infected from the first attempt to use diesel from the old agricultural tank.