Bamboo charcoal (BC) was used in an anaerobic ammonium oxidation (anammox) process used for synthetic wastewater treatment with the aim of evaluating its use as a biocarrier to reduce the cultivated anammox seed sludge (CASS) dosage. The CASS dosage was reduced by more than 50% after BC was added to the anammox reactor. Furthermore, the time required for the start-up of the anammox reactor under the experimental conditions was reduced about six weeks after the addition of BC. A genetic analysis of the organisms in the granular bed revealed an abundance of Kuenenia stuttgartiensis and uncultured bacterium clone KIST-JJY001 enriched in the reactor.