Sphaeramia nematoptera is a small, deep-bodied cardinalfish that trades the drab silver of many of its relatives for a genuinely striking color pattern. The head is yellowish to greenish and dominated by large orange to red-orange eyes, a broad dark vertical bar divides the body at midpoint, and the silvery rear half is dusted with orange-to-purple spots. Adults reach roughly 3.5 inches. The species ranges across the tropical Indo-Pacific from Java toward Fiji, north to the Ryukyu Islands and south to the Great Barrier Reef, where it favors sheltered bays and lagoons crowded with branching coral. Males are mouthbrooders, and wild fish form aggregations that break into distinct pairs during reproduction.

A well-established marine aquarium of at least 20 gallons suits an individual, and stability matters more than volume alone for this fish. Build the layout around shelter: abundant rockwork, caves, ledges, and branching structures positioned next to open water that the fish can hover in. Its swimming style is slow and deliberate rather than powerful, so low-to-moderate or moderate circulation serves it far better than turbulent, high-energy flow. Arranging the aquascape so that shaded overhangs sit within easy reach of a feeding zone helps a newly introduced specimen settle and come out to eat.