It says to not use flammable or corrosive liquids. I'd think vinegar would be OK. The tank is stainless but I'm not sure of the quality of stainless. Almost any cleaning solution should work. I was surprised at the job just water did so a bit of dish soap would probably work wonders.
I would try a carb though you'd likely have to do it half at a time. The tank looks to be large enough to lay the carb on it's side & get most of it in the solution. Run a clean cycle on one side then flip it over & run another. The size of the tank is ~9.75"Lx5.75"Wx2.75"D.
