As a general rule, whenever diesel and water come into contact in a fuel tank microbes will start to proliferate. Whether it is bacteria, mold or other fungi, unless this growth is held in check the result will be clogged filters, tank sludge and injector failure.
Water is heavier than diesel fuel and therefore accumulates at the bottom of a tank. No matter how well maintained the fuel tanks are aboard a yacht, there is usually some amount of free water sitting on the tank bottom. This water can come from a variety of sources:
Read more: http://www.the-triton.com/2015/03/even-well-maintained-fuel-tanks-have-microbial-growth
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