Algae will only grow at the fuel/water interface. If you have no water in your tank, you don't need any biocide. If you do have water in the tank, you still don't need biocide, you need to empty and clean your tank!
In fact, where marine diesels are common, there are often fuel cleaning services that will come out, pump the fuel from the tank, filter it, and put it back. That is, of course, a pricey service, but perhaps well worth the cost.
I have seen some very old diesel fuel and jet fuel (JP/4), and never noticed any deterioration.
I would say if the fuel and the tank are clean, don't worry about it.