2"x25"x72" (TxWxL)
=3600
Then divide 3600 by 28.88 because there are 28.88 cubic inches in 1 pound
=3600/28.88
=124.65
=125 lbs
It would be MUCH more cost effective to just lay the flourite where you plan on planting and where you don't plan on planting just put a gravel/sand that matches in colour.