The aim of this study was to explore the potential for reducing soluble N load in fishpond wastewater using naturally occurring denitrifying bacteria. Twenty-seven isolates were selected from in wastewater (liquid/solid) of catfish-ponds located along the Tien river, in the Mekong Delta, Vietnam in SW-LB medium (artificial seawater Luria-Britani medium) supplemented with 10 mM NH(4) and NO(3) and twenty-five isolates were identified as Pseudomonas stutzeri based on similarity of PCR-16S rRNA using universal primers and specific primers. Four isolates were effective in lowering Soluble N (NH(4), NO(2) and NO(3)) levels in fishpond water from 10 mg/L to negligible amounts after four days. Further experiments are underway to determine the fate of N lost from Solution and the relative activity of ammonia oxidation, and nitrite and nitrate reduction by P. stutzeri isolates. (c) 2009 Elsevier Ltd. All rights reserved.