Codium isthmocladum is a tall species in the popular codium family of seaweeds. Capable of branching out to 6 inches wide and 8 inches tall, it is one of the larger warm water species of codium. Its branches have a spongy texture, and are covered with small translucent hairs which give the macroalgae the appearance that it is glowing. Capable of living under low-moderate light, it will grow strongest in moderate to high lighting. The shade of green it takes will depend on the lighting it receives, turning darker with the more light that it is exposed to.
Unlike Codium fragile which has made its way into the hobby, Codium isthmocladum is a warm water species, and does well within the reef tank.The stalks are thin, and about 4-5 inches tall. They grow out to full size relatively quickly.