I to think that polishing is an odd term for cleaning fuel. I do have a few thoughts and observations on it tho. First some thoughts. The little Walbro pump that Cap Will suggests just won't move much fuel (great pump otherwise, I use and like them for priming) and a good sized gear pump is much better. All pumps should be on the outlet side of the first filter, never unfiltered, unless it is a centrifugal. That brings up another observation. I left a cover off on one of my tanks (aluminum, 600 gallon) and got some rainwater in it from deck runoff, unbeknownst to me for several weeks. The tank had been previously spotless, never having any water in it since new, installed by me. Befor that, With a flashlight you could see thru red fuel to the shiny bottom. This was summertime. In that time it developed lots of goop, crap, black stuff, gunk, etc, and generally looked like a 20 year old never cleaned diesel tank. I could see the water at the bottom in places. I have a 1/3 hp centrifugal pump plumbed into the bottom of the tanks that pushes fuel thru a RCI 1000 fuel processor. I have a hose attatched with a nozzle that can be used to spray each baffled section of the tanks. I completely cleaned the tank, several times, transfering the fuel back and forth to the other tank, using the spray nozzle, thru the RCI and back thru a 30 micron water seperating filter unit. The tank is CLEAN. I got no water, notta, none, in either filter. I am assuming the centrifugal pump emulsified the water enough that the filters didn't catch it, but I don't know that for sure. I will see if the water falls out of suspension to verify my thoughts. I also have a large gear pump that pulls fuel thru the filters for normal fuel circulation so when the water falls out I will try it. The centrifugal is great for moving fuel fast but maybe not as good for filtering. My thoughts on a cleaning system are that you can build a good one for fairly cheap. I just bought 2 excellent quality sealed 12 volt fuel transfer pumps (PBL industries, FP12) for 60 bucks each. A 250 foot partial spool of 5/8 inch ID marine rated fuel hose on ebay for $175, 2 sets of 2 BIG filters (Davcos, made for DetroitDiesel) with valves, on aluminum plates, at $250 each, throw in enough stainless clamps and valves and the whole system for two tanks won't be $1000. And, it can move a lot of fuel. If you get in a good beam sea you could really "polish" your fuel. This will be installed on a friends sportfishing boat. I will admit to being a compulsive shopper, and very frugal, but anyone with a little knowledge can do even better, and maybe cheaper.