Tank contamination known as diesel sludge is an algae-like substance in which cells adhere to each other on the tank surface or at the fuel water interface. The sludge settles to the bottom of a fuel tank and can clog filters when the vehicle is fueled.
What causes black algae in diesel fuel?
Loss of sulfur in the fuel (so there's nothing to keep it from growing) makes any free water in the tank a breeding ground for this fuel "algae". ... Just as little as a quarter-inch layer of water at the bottom is plenty enough for microbes and diesel fuel algae to grow and thrive.
