Never hurts to do a search of past threads on your topic.

A search using 'gas tank cleaning" found this thread which should get you started on some ideas.

http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=22;t=005616#000000

Others may chime in with more info.

Hope this helps.

"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson