Recirculating Aquaculture Systems (RAS) require careful selection of species to optimize growth, health, and sustainability. Species chosen for RAS must be adaptable to high-density environments, capable of thriving in controlled conditions with consistent water quality parameters. Common choices include species such as tilapia, trout, and shrimp, as they have proven resilience and rapid growth rates. Considerations also include water temperature, oxygen levels, and tolerance to waste products, ensuring the species selected can efficiently utilize available resources. Proper species selection not only maximizes production but also minimizes environmental impact in RAS operations.