Multiply your total surface acreage by the average depth (in feet) to get the total acre feet of water. So, if your pond is 3 acres and the average depth is 6 feet then you have 3x6=18 acre ft. The trick is knowing, and not guessing, the average depth. Not sure it matters to the muck reducing bacteria because it may be impossible to put too much but I'm not familiar with those products.

1 ac pond LMB, BG, RES, CC