So I pulled the strainer out of the 82 300 yesterday.the pre-filter was trashed so I figured the tank was a mess. Strainer was clean and no debris or "tank herpes".. which by the way I thought was hilarious term. Yet the pre-filter had what almost appeared to be mud. I looked at several images of the tank online..are there any crevices or valleys that aren't the lowest point in the tank?the only thing that I can figure is that the filter had trapped a small amount of water which then allowed algae to grow during its long-term storage?

Crud can lurk in the fuel strainer, in fuel sender, on the upper walls if the fuel tank, and in the fuel lines.

The fuel hoses can rot from the inside out.
The loose rubber debris will coat the lower half of the horizontal run of the metal and rubber fuel lines.

Fresh fuel will re-suspend this crud causing fuel filter clogs.
Good idea to additionally: replace all the rubber fuel hoses, pull and clean the fuel sender, carry spare fuel filters (and the tools to install them),
and to treat the fresh fuel with Biobor biocide and StarTron diesel fuel tank cleaner.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Thank you for the brand names on the biocide. I put my finger up in the tank around the strainer area, it was very clean inside. I'm getting ready to go put a few miles on it right now.

Startron for diesels does not just kill the stuff it has an enzyme that breaks up the dead so that the pieces are so small that they will actually pass through both filters. That reduces the chance that you have do several filter changes before the issue is settled.

Be sure to read the label so that you get the right one and or go to the Stratton website.

Algae Clogged Filter Pic StarTron WORKS !

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84 300D, 82 Volvo 244Gl Diesel