What the black gunk actually is does not really matter. I have been told it contains live bacteria, its dead bacteria, its the waste products from bacteria metabolism (bacteria poo ! I like that one) , semi decomposed or oxidized fuel, etc. All descriptions have one thing in common, Decomposed Diesel.
Whether the bugs are slow breeders or fast, if you get a bad load of fuel, you will soon have a problem.
We have had 4 lots of contamination in 30 years. Every time we have changed our fuel supplier and got rid of the problem.
Our bulk overhead tanks are over 40 years old and we have not had a problem in the last 6 years (touch wood).
If I was the OP I would drain the tank, put in fresh clean fuel from a different gas station with some sort of additive to clean it, replace Both filters & keep my fingers crossed. Dont try & re-use the contaminated fuel in the car, while it may work most of the time , its not worth the risk!
I dont use snake oil additives to fuel on a regular basis or some fandangled piece of junk attached to the fuel system, they are placebo's, it shouldnt be necessary. In some marine applications it may be. Regular road diesel should not need that stuff.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving