Some interesting things learned from Parker, the manufacterer of Racor
Diesel fuel will absorb small amounts of water and hold it in solution.
The amount of water that will remain in solution is dependant on temperature.
On a daily basis fuel tanks warm and cool. As the fuel cools a small amount of water will fall out of solution.(depending on humidity etc)
Racor filters can collect the smallest bits of water when the fuel is fed through at a very slow rate.
Parker is recommending that a slow flow (oz/hr) be pumped through racors in the evening as the tank cools.
Using this protocall there should never be any accumulation of water in the tank and no algae.
The only posible fuel treatment would be a solvency addative to minimize varnish
formation and if you have a mechanical diesel maybe a cetane improver.
I like this idea a lot but my fuel turnover is high enough to not bother.
Parker does make the pump, a crystal driven diaphram pump that uses so little power, you can leave it on.
The idea here is to keep the fuel dry, by any means. With dry fuel a polisher is never needed.