dosing based on freshwater volume

[chuffgod]

im new to mycodo and all coding in general. i have built a system to control grow room irrigation and environment. iv gotten a good bit figured out. now im trying to figure out how i can command my atlas scientific peristaltic pumps to dose nutrient volumes based on fresh water fill volume into a reservoir. things like silicon need to be added before nutrients and can not be controlled with the ec/ph controller.

i guess what im looking for is someone to point me to some existing code that can do this. in the mean time ill be spending my nights trying to learn to do it my self lol