The term 'brilliant fish' refers to four different species of fish: OPAH (4 letters), tetras (6 letters), tetra (5 letters), and opahs (5 letters). OPAH is a large, colorful fish found in the Atlantic, Indian, and Pacific Oceans. Tetras are small, freshwater fish native to South America. Tetra is a genus of small, freshwater fish found in tropical and subtropical regions around the world. Opahs are large, deep-bodied fish found in the Atlantic, Indian, and Pacific Oceans. All four species of brilliant fish are known for their vibrant colors and unique shapes.