The one that is almost missed. An alga that hides in the shadows. Red thread algae grows thin, red, thread-like fronds a few centimetres long, branching occasionally but mostly just drifting in the current. It does not demand attention or wave its arms. It just hangs there, a fine red tangle in the shadows, visible only if looked at closely. An alga that does not want to be seen. What makes it special is the fineness. The fronds are only a few cells thick – a single layer of cells in a tube-like structure. Delicate, almost invisible, easily torn by a careless hand. But also tough, able to survive in the low-light conditions of the shaded reef. A paradox of fragility and resilience. Often found growing on other seaweeds – an epiphyte, a plant that lives on another plant. It clings to the fronds of larger kelps, using them as a ladder to reach the light. It does not harm its host. It just hitches a ride. An alga that is a passenger. Reproduction happens by releasing spores from specialised structures on the fronds. Spores are carried by currents and settle on nearby surfaces to grow into new plants. Red thread algae provides habitat for tiny invertebrates. Microscopic crustaceans hide among its threads. To find red thread algae is to look closely at the reef. The reef is shadowed. The red thread hangs, fine and red, drifting in the current. A magnifying glass reveals the threads, the tiny crustaceans hiding among them. The alga does not know it is beautiful. It does not know it is a micro-forest. It just wants to catch the light.