It says to use 5ml per gallon, but i only use half of that. And I only used it during the summer when my water temps were above 75 for long periods of time.
I only use about 2.5ml per gallon and only put about 5ml in 3 gallons. It's very strong and I only use when my water temps are above 75°...
I know this is 8 years later, but I hope you've found Soythern Ag GFF. Way better and ALOT stronger so you don't have to use as much. It has 98% of the bacillus rather than like .09% or what ever it is lol.