In this study, an operational method of switching acetate media to ammonium media after the formation of stable acetate-oxidizing biofilms (ACAM mode), was developed. The results showed that the start-up time was shortened to 48 days in the ACAM mode compared to the AM (always ammonium media) mode (> 120 days), and an ammonia removal rate of 82 +/- 3% was achieved successfully and sustainably in the ACAM mode during the following long-term operation of more than 2 months. Moreover, the ACAM mode was more efficient in enriching both electroammox bacteria and electricigens with Ignavibacteriaceae, Geobacteraceae and Nitrosomonadaceae as dominant families, which could favour the formation of high-performance electroammox biofilms. Thus, the ACAM mode might promote the widespread implementation of the electroammox process.