Outer Limits 4x4 Board

I decided to investigate the cause of the dirt that was appearing in the glass fuel bowl. It only occurred when running the Long Range (175ltr) tank. After removing the tank I found the inlet strainer completely clogged with junk. When I shone a torch in through the inlet hole the bottom of the tank was covered with a brown scale or algae type substance.
I managed to get the hose in and remove most of it but was wondering is there a chemical treatment I can put in the tank to remove the scale from the hard to access areas before I reinstall it.
What about a radiator repair place can they chemically clean fuel tanks?

Get a packet or 2 of small nuts, and drop them into the tank, swirl/ agitate tank, then remove.
If its a diesel tank, put some diesel into a kero style cleaner gun, and flush out.
Use magnet to remove all of the nuts that dont drain out. Helps to count them.

Add some biocide to the tank, put in a few lts, and let it be for a week, then drain off some to check for fuel condition, and off you go.

Trains

Yes, thanks for the ideas. The fuel tank empty weighs about 60kg so no throwing in a few nuts and agitating. I have cleaned out as much as possible of the algae formation with the hose. I have purchased a chemical from Repco called Chemtech that is a strong diesel biocide & kills algae. I think the algae has been there for a while & since I have been running 100% biodiesel it has removed it from the tanks inner surface and pushed it through to the filter. The 1 ltr of Chemtech should treat about 4000ltr.