A method includes operating a downhole acquisition tool including a guard probe and a sample probe in a wellbore that contains a fluid that includes a native reservoir fluid and a contaminant. The method also includes receiving a first portion of fluid into the guard probe and a second portion of fluid into the sample probe, estimating a contamination level of the first or second portions based on a fluid property of the respective first and second portions, determining an initial guard flow rate of the first portion, determining an initial sample flow rate of the second portion, using a processor to adjust a guard flow rate of the second portion over pump time after the contamination level of the first portion is at or below a contamination level threshold, and adjust a sample flow rate of the first portion based on the adjusted guard flow rate and total flowrate.