A system for matching the hydrocarbon reservoir inflow with the outflow of an artificial lift system utilizes an apparatus which makes real time fluid level determinations and inputs the observed fluid levels into a processor which controls the speed of a motor which operates a subsurface pump, so as to increase hydrocarbon production. The apparatus which makes real time fluid determinations is installed such that a gas emission port and a pressure wave receiving port are placed within the tubing-casing annulus.