A separation agent for avoiding and/or destroying microbial growth in a store for a liquid hydrocarbon is provided wherein an interface between a phase of a liquid hydrocarbon and a phase of water can be reduced. The agent has a density which is higher than the density of a liquid hydrocarbon and lower than the density of water. By using the agent, simple, economical, efficient and long-lasting avoidance and/or destruction of microbial growth in a store for a liquid hydrocarbon is ensured. The avoidance and/or destruction includes inhibition of the increase in the microorganisms already present in the store and/or the killing thereof and a high quality of the respective liquid hydrocarbon is ensured. A method for avoiding and/or destroying microbial growth in a store for a liquid hydrocarbon, and a store for a liquid hydrocarbon which is suitable for the avoidance and/or destruction of microbial growth are also disclosed.
