1 Vial per 250L if I remember its been a while since Ive used it. You put in 1 vial of the bacteria one week say after a water change, then the next week 1 vial of the carbon source. I was concerned about over dosing at the beginning as 1 vial is way more than my system needed but never saw any adverse side effects from it.
While I was using the stuff I was like, hey this stuff doesn't do anything. Placebo. Not until I stopped using it did I realize I missed it........