Two batch mesocosms were created on site in Da Nang, Vietnam to reduce nutrients in wastewater from fish processing factories. The mesocosms contained either activated carbon or coconut fibre which in earlier studies has shown promising results in wastewater treatment. Three aspects of the materials were compared; Chemical content, which measured levels of COD, total-nitrogen and total-phosphorus. Rate of biofilm formation, where biofilm were measured visually and through weight. The last aspect was microbiological presence where fours species of microorganisms were cultivated. The experiment showed no obvious difference between the materials but concludes that this is an experiment that could and should be developed further.