Regarding portable filters you would use at the fuel dock, this is a cut and past from a previous post we made--"We've had good luck with the Mr. Funnel filter, we use the largest one with 2 filters in the bowl. The flow rate is good and it allows you to reasonably fill your Amel tank at the fuel dock at 12 gpm. The Mr. Funnel, West Marine, and Racor RFF are the same and all made by Shurhold. You can test it periodically by filling about 1/4 full with water and confirming that none passes, with more water, say 1/2 there is enough pressure to push the water through. Can also use it for a contaminated outboard tank but take precautions with gasoline! Racor says it filters down to 50 microns http://www.parker.com/literature/Racor/Racor_Fuel_Filtration_-_Fuel_Filter_Funnels_-_7568.pdf " The fact that Racor is marketing a version is a good endorsement I think.
Regarding a fuel polishing system. I would urge you to take a close look at "fuel purifiers"..We used an RCI fuel purifier for about 8 years on our Santorin and we drained a significant amount of gunk out before if got to our Racors. We are presently using a similar MLS which we purchased in the Netherlands. Professional fuel polishers tend to use these kinds of units with their portable polishers and they are also popular on earth movers, buses, trucks, etc.There are not filters to drain and they don't clog.. They say they remove 99% of the water and particulates and you just drain it out into a cup and discard. I would just put it inline ahead of the Racors and would not bother with a circulation pump or anything else. As noted in this discussion, there is considerably more diesel fuel pumped through the fuel system than is used by the engine. Excess fuel is frequently used to cool the injectors. Universal Fuel Purifiers | RCI Technologies
If you ever wonder how fuel polishers do their work without going through scores of filters the answer is that they use fuel purifiers. Portable Fuel Polishing Units | RCI Technologies
I used to provide a website for a diesel shop in Maryland and they gave me a deluxe on-board polisher for my Santorin which you can read about in the link that follows--but I think the design was over-kill and on my Super Maramu I use just an initial inline fuel purifier (rated for 300 hp diesels, I think) Marine Diesel -Advanced Fuel Filtering and Conditioning Onboard Fuel Polisher
Again that system was real overkill and I don't happen to believe in the Algae-X they threw in....
Regarding the 2/10/30 micron, IMHO the most important thing is to see that your suction pressure remains low on your Racor. If you don't have one you should install a gauge. In a cumulative 11 years of using fuel purifiers I don't think I ever really needed to change a Racor filter. They were always clean when I removed them on a scheduled basis and the suction pressure never built up.
Regarding additives I have always been a fan of Stanadyne Stanadyne Additives
They are in the diesel pump and injector manufacturing business and it is what they market Stanadyne
Bob, KAIMI #429, Marmaris, Türkiye