Basic question about DWC, please help

I was wondering if someone could tell me the ideal range of liters of air per minute I want my air pump to do for each plant? Any answers are appreciated

Was growin for a # of years DWC. Changed nuts every week, had 2 Air stones 6-8' long and the air pump had a surplus supply of air. As long as there is enough DO in the buckets you don't worry about the liters