Routinely, I depend on the Racor, conditioner and biocide . I've also set up a cleaning loop using 3-way valves, another filter/separator, and an electric fuel pump I run now and then when under sail and sloshing fuel around in the tank. A couple of times, though, I've had to pump it out of the tank into containers, let it settle half a day, then pump it back in pulling it off the top and stopping before it reaches the level of water at the bottom. I don't want to have to do that a lot, so I try not to let the boat be idle for more than a few weeks at a time. Running the motor half an hour every week or so, even when tied to a dock, seems to avoid most of the problem.