The sargassum frogfish can attain a maximum length of 6 inches. The most interesting characteristic that members of this group possess is a first dorsal spine that has evolved to become an important component in the feeding process. This spine, known scientifically as an illicium, is thin and elongate and is equipped at its end with a fleshy tip, known as an esca. When the frogfish sees a fish of edible size, it erects the spine and moves it about. The moving dorsal spine acts to lure prey to within striking distance.
Frogfishes inhabit rocky and coral reefs, sea grass beds, pier pilings, and sand and mud bottoms.
What makes the sargassum frogfish so unique is that it lives among the fronds of floating sargassum algae. You may have heard of the Sargasso Sea, so named because of the large concentration of sargassum that occurs in this area. The sargassum frogfish's color pattern and the skin flaps that cover its body help it to blend in with its natural surroundings. The color pattern, which typically consists of brown stripes and blotches on a tan background, is highly variable and can suddenly fade or intensify to match the fish's surroundings or communicate its mood. Even though the sargassum frogfish is always found in association with this macroalgae in the wild, it can be kept without it in the aquarium.