It's four tanks. Three 75gs and one 65g I have to pick up next Friday. Works out to 25 bags which equals 337# for 3" Flourite per tank. Two extra bags for left over for my 10gs and 20gs that I want to plant as well.
Then there's a 1¼" layer of aragonite sand to be mixed into the top layer of the Flourite.
Oh yeah I feel your pain! I read a thread here recently that a complete rinse was not necessary or particularly good. For obvious reasons I rinse mine.
I've given up all my tricks for keeping the "dirt" in the Flourite. Most of that stuff is just minute particles of broken clay produced from the larger pieces rubbing around against each other.