Ok i just broke down and purchased a GHL Doser 2.1 (4 heads). Now i know the main 3 for dosing is Calcium, Alkalinity, and Magnesium. But seeing i have a 4th dosing pump I'm curious to what others dose besides the common 3 listed above.
Is there any 1 thing that comes of most importance to dose for a 4th pump?
Is there any 1 thing that comes of most importance to dose for a 4th pump?



