Modern aquaculture technologies are made with the help of recirculation systems, which require the use of innovative and highperformance solutions for the treatment of recirculated water. Aquaculture recirculation is essentially a technology for growing and developing fish or other aquatic organisms by reusing water for more intensive fish production. The technology is based on the use of mechanical and biological filters, and this ecological method can be implemented for any species cultivated in aquaculture, such as fish, shrimp, mussels, etc. The scientific paper presents a brief summary of the control and solution of the main problems faced by water recirculation systems.

The intensive application of pesticides and chemical fertilizers, in the context of the continuous development of agriculture, has led to a high level of environmental pollution and a serious deterioration in soil fertility. In an attempt to reduce all these negative effects, classical agriculture is moving towards sustainable agriculture. An ecological alternative to the use of chemicals is the application of organic fertilizers. One of the ecological sources is aquatic plants. Often considered invasive due to their rapid development, aquatic plants have a real potential in sustainable agriculture. This review presents the use of aquatic plants pistia stratiotes, eichhornia crassipes and salvinia molesta as organic fertilizer in sustainable agriculture.