Accumulation of Total Ammonia Nitrogen, Unionized Ammonia and Nitrate in the Recirculating Aquaculture System

Abstract

This research was to study the accumulation of total ammonia nitrogen (TAN), unionized ammonia (NH₃) and nitrate (NO₃) in the recirculating aquaculture system to be used in consideration of the appropriate water change for fish farming in the treated recirculating water system using biofilter treatment. In the experiment, two stocking tilapia densities were tested as follows: 30 fish/m³ and 40 fish/m³. To reduce the accumulation of toxic substances form fish waste, the water from the test ponds were changed every 2 weeks. The study revealed that, the accumulation of TAN NH₃ and NO₃ in the fish ponds were proportional to the number of fish densities in the ponds. If the water change cycle was scheduled at 2 weeks, the accumulation of TAN and NO₃ was acceptable. However, the accumulation of NH₃ was the main factor that must be used to determine the water change interval. That was, water should be changed every 1 week to reduce toxicity to fish.