Fuel tank algae
You do not have to remove your tank to clean it. Just look up a service that does "Fuel Polishing". You must be docked for this operation with 110vac power available. The Polishing consists of a large external filter with hi-pressure pump output. The system sucks fuel out of tank near bottom and filters it. It is then discharged back into the tank at about 1000psi. This stirs up the crud and suspends it for pickup by the suction side of the system. It''ll take a few hours to get it clean--but it is very easy. I''ve had it done in Mexico and diesel down there can get cruddy if not treated.