Common name: Manila Grass

General information

Actinotrichia fragilis, commonly known as Manila Grass or Bristle Brush Algae, is a species of calcareous algae found in coral reef environments. This alga is characterized by its stiff, brush-like tufts that can range in color from green to brown. It is a member of the family Galaxauraceae, which includes a variety of other reef-building algae species.

As a calcareous alga, it contributes to the structural complexity of the reef by depositing calcium carbonate within its cell walls, thus playing a role in the growth and maintenance of coral reefs. Its presence in an aquarium can be indicative of good water quality, as it tends to thrive in well-lit, high-flow areas with stable conditions.

Care

For hobbyists looking to cultivate Actinotrichia fragilis in their reef aquariums, providing strong lighting and moderate to high water flow is essential. This alga prefers stable water parameters, particularly calcium and alkalinity levels, to support its calcification process. It can be a beneficial addition to a reef tank, as it can help with nutrient export by uptaking dissolved organic compounds.

Symbiosis

While Actinotrichia fragilis does not have the same type of symbiotic relationships as some corals or anemones, its structure provides microhabitats for small invertebrates and can be a grazing area for herbivorous fish. It can also act as a natural competitor against nuisance algae by occupying space and utilizing nutrients.

Habitat

Actinotrichia fragilis is commonly found in the Indo-Pacific region, particularly in shallow waters where sunlight is abundant. It is often seen growing on dead coral substrates, rubble, or even on live corals, contributing to the reef's biodiversity and structural complexity.