I guess we agree on the bottom line....the biocide cleans the tank of anything bacterial. I am dubious about the grit but since I cannot get in there and swim around I'll have to take your word about it.

To me the only grit I would expect to see would be basically dirt and dirt products which would come mainly from the air. If you keep a cap on your fuel tank you should have a minimum of that.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.