The invention relates to devices for purifying water in aquaculture tanks. The technical result of the invention is an increase in the degree of water purity and an increase in the lifespan of a biological filter medium. A system for thoroughly purifying water for aquaculture tanks includes, arranged in succession, a primary mechanical water purification compartment(s) in the form of a tank filled with separating lamellae arranged in sections on a false bottom, a compartment(s) for biologically purifying water in a fluidized bed, said compartment being in the form of a tank filled with a biological filter medium disposed on a false bottom, wherein a device for aerating the biological filter medium is disposed above the false bottom and below the layer of a biological filter medium, and a secondary fine mechanical water purification compartment(s) in the form of a tank filled with separating lamellae having a smaller clearance therebetween and being arranged in sections above a false bottom； furthermore, all of the tanks are oriented vertically and have a height that is 3-5 times greater than the equivalent diameter of the cross section of the tank, in each section the false bottom is in the form of a perforated plate, a compartment that is free of equipment is disposed below the false bottom for dirty water, collectors for catching mechanical impurities are disposed beneath each tank, and purified water outlets are disposed at the top of each tank.L'invention concerne des dispositifs pour traiter l'eau dans des récipients d'aquaculture. Le résultat technique consiste à augmenter le degré de purification d'eau et prolonger la durée des ressources de fonctionnement de charge biologique. Le système de nettoyage complet de bassins d'aquaculture comprend une ou plusieurs section(s) de purification mécanique primaire se présentant comme un récipient rempli de lamelles de séparation qui sont disposées section par section sur un faux fond, des compartiments de nettoyage bio
