This is my dumb question. What kind off algae, or anything else, grows in diesel? Is this related to Bio fuel?
Actually, a good question. Algae/microorganisms do not grow in clean diesel. And to my knowledge not in B5 or B20 either.
They DO grow at the water/diesel interface if there is water present. It starts as black particles in the primary fuel filter/water separator. In bad cases, long, stringy "black slime" is formed.
There are two ways to get water in diesel-- and you can reduce your chances by doing a couple of simple things:
Fill at stations with a lot of turn-over-- if 18 wheelers fuel there, likely the fuel has not sat in the station's tank for months.
Do NOT fuel if you see a fuel truck delivering fuel to the station. Those very high volume "dumps" into the tanks stir up any water or dirt in the tank.
When storing your coach:
1. Fill fuel tank to reduce condensation. Any air in the tank when you park will condense its moisture out when the dew point of the air in the tank is reached. So, if you have 50 gallons of hot humid air in the tank and the temperature drops below the dew point, you can condense a cup or more of water. That water, being heavier than diesel falls to the bottom of the tank, where the diesel above keeps it from ever evaporating.
2. If storing the fuel for more than 2 months in the summer or 3 in the winter, add a BIOCIDE. Biobor JF is a very common one. Where you live in Galveston, you can find it at any marine store, as boats have the same issues storing diesel. Biocides will kill any of the microorganisms present, but their "dead bodies" will still be caught and can clog the fuel filter(s).