With the 2HR Aquarist APT-EI, the famous nutrient dosing approach pioneered by Tom Barr is now available in a ready-to-use concentrate that removes the guesswork from trying to recreate this powerful and sometimes elusive formula.

An overview of the EI methodology can be found here.

Dose 5ml per 100L 3 times per week or 2ml per 100L daily.
FAQ here.