[Fulltiming]

While it is technically true that algae needs the presence of water to grow, it is easy to get moisture/water in your diesel fuel. Changing temperatures will cause the moisture in the air inside a diesel storage tank, be it the dealers underground tanks or your fuel tank, to settle out and form a water/diesel fuel boundary layer. That is were the algae will grow. Of course if you spend all your time in the desert, keep your tank full all the time and buy fuel from stations in dry areas that are meticulous about controlling moisture in their tanks, the probability of getting a growth of algae is greatly reduced. However, one bad tank of diesel fuel can introduce significant water into your tank. Fuel at the same time that a station's tanks are being fueled from the tanker can result in the diesel getting stirred up in the station's tank and pumped into your vehicle. Now you have contaminants in your diesel tank, including water, potentially algae and debris. It will start filling up your fuel filter with slime very quickly.

Been there, done that.