I dont know about using creek gravel but I have use glass marbels. They dont spark so any fluid you use will be ok. I have used chemtool carburator cleaner. The gallon can. works well but use a well vented area. I did this one time on a motorcycle tank and straped it to a paint shaker. CLEANED THE CRUD OUT OF IT!!!!!
I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"
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