Originally Posted by Saf
I cut my primary fuel filter open and it was black like oil, is this normal and how does clear fuel turn black?
You have a microbial infestation, its caused by water in the fuel. Some people call it algae, it's not as that is a vegetation and it needs sunlight to grow. Treat the fuel with a shock treatment of an anti-microbial additive like BioborJF to kill the microbes, then use something like Startron Tank cleaner to get rid of the black gunk.