I made a DIY fuel polisher. Full episode coming soon so be sure to subscribe to see it.
I show how to clean the fuel tank and why.

The pro way would be

Cleaning diesel bug (microbial contamination) from a fuel tank is essential to maintain the efficiency of the fuel system and prevent potential damage. Here are the general steps you can follow to clean diesel bug from a tank:

Identify the Contamination:

Look for symptoms of diesel bug contamination, such as clogged filters, reduced engine performance, or the presence of sludge in the fuel.
Isolate the Tank:

Disconnect the tank from the fuel system to prevent further contamination.
Drain the Tank:

Safely drain the remaining fuel from the tank. Dispose of the contaminated fuel according to local regulations.
Inspect and Clean the Tank:

Inspect the interior of the tank for sludge, debris, or microbial growth. Use a flashlight and, if possible, a borescope to thoroughly examine the tank's surfaces.
Clean the tank by wiping down the interior with a suitable cleaning solution. This may involve using a mixture of diesel fuel and a biocide or a specific tank-cleaning solution.
Remove Sludge and Debris:

If there is significant sludge or debris, use a hand pump, vacuum, or suction device to remove it. Be thorough in removing all contaminants.
Biocide Treatment:

Apply a diesel biocide to kill any remaining microbial contamination. Follow the manufacturer's instructions for the correct dosage and application procedure.
Tank Drying:

Ensure the tank is completely dry before refilling it with fresh diesel. Moisture can contribute to the growth of diesel bug, so take measures to eliminate any remaining water.
Filter Replacement:

Replace fuel filters to ensure that any remaining contaminants are removed from the fuel system.
Refill with Clean Diesel:

Refill the tank with fresh, clean diesel fuel from a reliable source.
Monitor and Prevent:

Regularly monitor the fuel system for signs of contamination. Consider adding a fuel conditioner or stabilizer to prevent future microbial growth.
Professional Assistance:

If the contamination is severe or if you are unsure about the cleaning process, consider seeking professional assistance from a fuel system cleaning service.
Always follow safety guidelines and use appropriate personal protective equipment when working with fuel and cleaning solutions. Additionally, consult with your engine or equipment manufacturer for specific recommendations related to your system.