I installed daytanks in my boat as that seemed to me to be the only reliable solution for my 30+ year old tanks.
The gunk (asphaltenes, biological debris or whatever its is) that accumulates over time in boat diesel tanks seems to stick to the walls of the tank and is released to clog the engine
filters at the most inopportune times: in a seaway.
Multiple filters that can be switched over are are not always effective because the amount of gunk released can overwhelm not just the first filter but also the back-up.
Inspection ports are often not effective because the baffles limit the access for cleaning
the inside of the tanks.
Fuel polishing can help but it is not going to remove the sludge sticking to the walls, bottom and baffles of the tank.
I question biocides that attribute the problem to algae as no algae is going to grow inside a dark tank.
So, for me, the solution was to install daytanks that I fill up with filtered fuel on a daily basis when cruising. (I also have a permanent fuel polishing system that I run while cruising when the motion of the boat shakes-up the crud in the tanks.)