Additives for Grey Water Holding Tank

As fulltimers we are often sitting for months at a time with the grey valve open. Even with wiping dishes and pans out before washing some food particles will wind up settling in the grey tank shower water not withstanding. The last thing I do before packing up to move is close the grey valve and run hot water till it's cool. Then drive 200-300 miles on our lovely roads and stop for the night, hookup the sewer hose and open the grey valve. If you have one of those clear elbows you'll be surprised at what comes out.