Balance Between Daily Water Renewal and Nitrate Levels in a Recirculating Zebrafish Housing System

In zebrafish housing systems with water recirculation, a daily renewal of at least 10% of the total water volume is generally recommended to preserve optimal water quality. Such aquatic housing systems often rely on reverse osmosis (RO) water. RO production uses large amounts of running water, a high proportion of which is then discharged into waste. A key parameter for water quality control is nitrate, the final transformation product of the nitrogen cycle in water. Here, we used this parameter to test whether daily water renewal could be reduced in our zebrafish housing system without impact on water quality. For 18 months, divided into four periods, we progressively reduced the rate of water renewal from 10% to 6%. We show that nitrate levels are not impacted when renewal rates remain above 8%, making it possible to significantly save on water in zebrafish breeding systems.