Any diesel fuel expands and contracts, and during contraction, room is left in the fuel tank for condensation (i.e. water accumulates inside the tank). Because water encourages microbe growth and because biodiesel naturally collects water, biodiesel is much more susceptible to algae blooms than standard diesel. Once a microbial bloom becomes large enough, it clogs injectors and fuel filters. Antimicrobial additives can help to discourage algae blooms in biodiesel.