Torch coral

Lore & Background

Euphyllia glabrescens is a colonial coral with a phaceloid formation of corallites 20–30 millimeters in diameter and spaced 15–30 millimeters apart. Its walls are thin with sharp edges, and the polyps have large tubular tentacles with knob-like tips. The coral can be a number of colors and is often bicolored with contrasting tentacles and polyp tips. This species is widely distributed but rare in the Red Sea and the Gulf of Aden, and uncommon through the northern Indian Ocean, the Persian Gulf, the central Indo-Pacific, Australia, Southeast Asia, southern Japan and the East China Sea, Micronesia, and American Samoa. It is found at depths of 1 to 35 meters in a wide range of reef environments. Its behavior includes the use of long sweeper tentacles tipped with potent cnidocytes, which are used for defense and competition.

Reader's Guide

Euphyllia glabrescens is a colonial, phaceloid coral with corallites 20–30 millimeters in diameter spaced 15–30 millimeters apart. Its thin walls have sharp edges, and the polyps bear large tubular tentacles with knob-like tips. The species exhibits a variety of colors and is often bicolored. It inhabits depths from 1 to 35 meters across a wide range of reef environments, though it is rare in the Red Sea and Gulf of Aden and uncommon elsewhere in its distribution. In the reef ecosystem, its long sweeper tentacles armed with potent cnidocytes allow it to compete for space. In the marine aquarium trade, it is a commonly kept species, with notable annual export quotas in 2005 of 28,000 pieces from Indonesia and 6,000 pieces from Fiji.

Did You Know?

• Its common name 'torch coral' comes from its long sweeper tentacles tipped with potent cnidocytes.
• In 2005, Indonesia fulfilled an annual export quota of 28,000 pieces of this species.
• In 2005, Fiji fulfilled an annual export quota of 6,000 pieces of this species.

The Reef Aquarium Ecosystem

A reef aquarium is a specialized marine setup that centers on live corals and invertebrates alongside compatible fish, creating a miniature tropical reef environment. Unlike simpler fish-only tanks, this system demands significantly more stable water chemistry, intense and tailored lighting, and turbulent water circulation. Every element must be carefully selected for compatibility, since the animals share a confined space. The livestock is housed in a primary display tank, often elevated on a stand to eye level, while mechanical equipment is tucked away in a sump below. A refugium may be included to cultivate beneficial algae and microorganisms. Lighting is chosen specifically for the types of coral being kept, and a canopy above the tank holds the fixtures while allowing access for feeding and maintenance. The entire arrangement is designed so that the display remains visually clean while the complex machinery operates out of sight.

Flow Requirements and Coral Placement

Water movement is a critical variable in any reef tank, and different corals have distinctly different needs. Torch coral, classified among the large-polyp stony corals alongside brain, bubble, elegance, cup, and trumpet corals, thrives in moderate flow conditions. This sits between the very low flow preferred by mushroom and polyp corals and the high, turbulent currents demanded by small-polyp stony corals like Acropora, Montipora, Porites, and Pocillopora, which mimic breaking waves at shallow reef tips. Hobbyists often target a turnover rate of ten times the tank volume per hour, equivalent to a full water exchange every six minutes, though this is a general guideline with many exceptions. The direction of water pumps significantly affects local flow speeds, and notably, many corals will gradually relocate themselves within the tank if the current in their immediate area is unsatisfactory. Flow speed, rather than simple turnover, is the critical measure for determining gas exchange rates and thus how quickly a coral respires and photosynthesizes.

Filtration and the Berlin Method

Biological filtration in a reef aquarium typically relies on live rock sourced from tropical reef zones or, more recently, aquacultured rock from Florida. Some keepers supplement this with deep sand beds to help reduce nitrate, a byproduct of incomplete nitrogen cycling, while others prefer a bare-bottom or suspended reef approach for easier detritus removal. Protein skimmers are a standard addition, using foam fractionation to draw organic waste onto microbubbles that overflow into a collection cup. Together, these elements form the Berlin Method, named for the city where it was first developed. In recent years, a refugium has become a common supplement, housing macroalgae such as Caulerpa prolifera or chaetomorphae, which absorb excess nitrate, phosphate, and iron while supporting beneficial zooplankton like copepods and amphipods. These tiny invertebrates, once returned to the display tank, serve as natural food for corals and fish. Conventional mechanical filters used in fish-only systems are deliberately avoided, as they trap detritus and generate nitrates that can stunt or kill delicate corals. Activated carbon may be added for chemical purification when needed.

Tank Construction and Overflow Systems

The physical structure of a reef tank is engineered around efficient water circulation. Many keepers choose a reef-ready or drilled tank, where holes in the rear pane allow water to drain into a sump or refugium. These drains are typically enclosed in an internal overflow apparatus of plastic or glass, housing a standpipe and a water return line. Surface water pours over the overflow, travels down the standpipe through PVC piping into the sump, and is then pushed back into the aquarium by a return pump. Alternatively, standard non-drilled tanks can use an external hang-on overflow that feeds water via continuous siphon. Tanks are built from glass or acrylic: acrylic offers superior optical clarity, lighter weight, and easier drilling, but scratches readily and can bow, with top bracing sometimes limiting access. Glass is heavier but more scratch-resistant. For larger builds, industrious DIYers have even used epoxy-coated plywood. The sump itself keeps bulky filtration equipment out of the display, maintaining a clean visual presentation.