This will sound snarky, although it isn't meant that way, but I use a fuel vendor that doesn't send me water.
So the real story is, I use Algae-x magnets in the main header from the tanks, and also in the fuel line to each generator. When I feel the need to buy lots of racors, I use Algae-x liquid fuel treatment in the tanks at twice the recommended ratio. When I really want them clean, I use Bio-Bor, and when I don't want to mess around, I use bio-diesel. Bio diesel will cure whatever ails ya, and it will pull the water out of your tanks, but if you have a real algae problem, you'll run a case of racors in a day. In my case, 5 or 6 cases of racors in a day. Then, you won't mess with it for another year.
I have a fuel polishing service available to me. I polished both my tanks and still was having problems. I had the polisher guy come back when I opened the tanks and there was a foot of algae sludge in the bottom. It came out with a shovel. I am not a believer in polishing fuel. Bio-diesel is the real thing, but it's going to clean your tanks like right now. When most folks switch a boat from diesel to bio diesel, they start with B-2, then B-10, then B-20, then B-50, then B-100, because using B-100 right off the bat will cost a bunch in fuel filters.