Oxygen etching reactions of silicon cluster cations and anions are studied with a fast-flow reaction apparatus. Ions incorporating silicon oxides are not observed as products in either the cation or anion studies. Magic clusters are identified as n=4, 6, 9, 13, 14, and 23 for the cations. For the anions, where there are no previous studies of oxygen etching reactions, magic clusters are found at n=18, 21, 24, 25, and 28. We note good overall agreement with past experimental findings in the case of cations, and with theoretically predicted structures for both anions and cations.