Abstract
The aim of the study was to follow the dynamics of changes in nitrogen and phosphorus compounds during intensive rearing of larval and juvenile ide, Leuciscus idus (L.), in a recirculating system. The study was conducted during two experiments of fifteen days. A shelf biological filter was used with 4 mm polyethylene balls as the filler. The results obtained are evidence that nitrogen and phosphorus can be removed successfully from water with biological filtration. They also confirm the need for fully controlling physicochemical conditions in order to determine the production capabilities of recirculating systems. Additionally, the results also demonstrated that it is possible to limit the impact of intensive fisheries production on the natural environment through the application of appropriate water purification systems.