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I poured in 4 gallons of vinegar and a half a container of table salt. This was with the block sitting in the barrel. Then I filled it with water to where it was approximately 4 inch above the top of the block which works out to about 40 gallons maybe 45.
My tank is a plastic 55-gallon drum that I cut the top out of.
This is the tank with the block sitting inside it. The apple vinegar bubbles like swamp gas coming up in a swamp. It forms a foamy crust on the top.