During the five-year period, 37 different species of fish were collected from the Rainbow River System. The study helps biologists tell how any impact, whether natural or man-made, is affecting the spring's ecosystem and ecology.

Rainbow Springs, one of Florida's largest and most beautiful first-magnitude springs, is home to a vibrant ecosystem of freshwater fish. In 2026, snorkelers and kayakers can easily spot several species in the crystal-clear, 72°F (22°C) water. The most common fish include Largemouth Bass, which often hover near the underwater vegetation, and various species of Sunfish (Bream) like Bluegill and Redear Sunfish. You will also frequently see Gar, identifiable by their long, needle-like snouts, and schools of Mullet jumping near the surface. One of the more unique sightings is the Bowfin, a primitive fish that has remained largely unchanged for millions of years. The state park and aquatic preserve work diligently to monitor invasive species, such as the Sailfin Catfish, which can damage the spring's banks. Because the water is so transparent, the "underwater forest" of eelgrass serves as a perfect nursery for these fish, making Rainbow Springs a premier destination for underwater photography and nature observation in the Sunshine State.