?? Based on what you described, you will need to have your fuel & tanks 'polished'
. Likely have more 'stuff' (algea) in the bottom of the tank(s). Any additives you add to rid the algea will also cause more to break free from bottom or baffles in the tanks
. Get it done correctly with a 'fuel tank polisher' and his cetrifugal pump. They need to access the tank through an inspection
port to properly agitate the stuff off the bottom, walls and baffles and then cycle all the fuel through the pump. Works really great. After your tanks are clean, use an additive to keep the algea on the down low and keep the tanks full of diesel