The removal of ammonia (NH3) through nitrification in intensive aquaculture systems is an important process as the total ammonia nitrogen (TAN, compromising NH4+ and NH3) concentration often is the key limiting water quality parameter in these intensive aquaculture systems. In this study, the performance characteristics of a suspension of nitrifying cells (named ABIL) have been explored This aqueous suspension contains a highly active, nitrifying microbial consortium and is stable for several months when preserved at 4 degrees C. Tests were performed in freshwater at lab scale (70 L, 20 - 24 degrees C). Results showed that the application of the consortium at a dose of 5 mg Volatile Suspended Solids (VSS) L(-1) assures a total removal of ammonium and nitrite species from 10 mg N L(-1) to below the detection limit within a period of four days. Experimentally, at a substrate level of 10 mg TAN L(-1), a rate of biological ammonium and nitrite conversion of the order of 0.3 - 0.5 g TAN g(-1) VSS(-1) d(-1) could be achieved by the consortium in the freshwater aquaria systems tested Provided adequate aeration and dissolved oxygen levels of 6 mg per L or more, no important intermediary nitrite concentrations were noticed Only a small amount of TAN was not found back as nitrate and might have been lost due to ammonia stripping After 12 months preservation of the inoculum at 4 degrees C, no important decrease in ammonium removal activity and only a minor decrease in the nitrite removal rate of the consortium were noticed.