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Related Articles: True or Stony Corals, Order Scleractinia, Dyed Corals,

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Quintessential Small Polyped Stony Corals, the Staghorns, Family Acroporidae, pt. 1

To: Part 2, Part 3

By Bob Fenner

Fiji Acroporids. The family Acroporidae make up most of the species and most of the biomass of the world's reefs. 

There is an artificial, albeit useful, convention amongst hobbyists distinguishing hard or stony corals (Order Scleractinia) on the basis of their apparent individual polyp size: Large and Small. Small Polyp Stony corals are made up of miniscule polyps generally borne on branching, encrusting or plate-like skeletons.

The artificiality of this arrangement is borne out in the membership of both SPS (Small Polyp Stony) corals and LPS (Large Polyp Stony) corals existence within the same families, sometimes genera. However arbitrary the division, there is general utility in the visual distinction of Small versus large Polyp corals. In a few words, SPS' prove harder to keep than LPS'. This is often cited as being due to the greater cleanliness and stability of environmental conditions where SPS' are found.

(Images #2,3: A LPS coral, Caulastrea furcata, Family Faviidae and a member of our family of SPS', Acropora cerealis. LPS' polyps are, well, larger than SPS')
Verticals (Full/Cover Page Sizes Available

(Images #2,3: A LPS coral, Caulastrea furcata, Family Faviidae and a member of our family of SPS', Acropora cerealis. LPS' polyps are, well, larger than SPS')

Indeed, as many of the popular LPS' are collected in shallow back reef areas, the majority of SPS' hale from reef flats to deeper offshore environs where there is definitely less silt, and more homogeneous light and brisk circulation conditions.

For the hobbyist there are obvious practical implications. SPS require more stable and optimized environmental conditions; strong lighting, high water quality and even temperatures. Nonetheless the smaller polyped scleractinians have many endearing qualities; subtle to brilliant colors, fast growth and a propensity for culture through fragmentation that endear themselves to advanced reef hobbyists.

Growing tips (colored) of a wild Acropora (cerealis?) in N. Sulawesi.

Amongst the stony corals, large, medium or small polyped, there are none larger, literally and figuratively than the Staghorns, Family Acroporidae ("Ackro-pore-id-ee"). This family contains the true corals number one and two most speciose genera (Acropora, Montipora). As reef builders the family rules supreme; their hermatypic colonies are the most important worldwide in terms of mass and volume.

Family Acroporidae, Classification:

Staghorn corals come in many shapes and all colors... and these traits can be highly variable per species. Most are typically branched, table-top shaped, or encrusting per type, but colors often ran the gamut of browns, whites to pinks, blues, yellows, greens, even purple, depending on growing conditions. As with other true or stony corals (Order Scleractinia) real determination to the species level rests on close examination of corallites (individual polyp skeletons), biochemical and genetic study. For aquarium identification, they are best labeled down to the genus ranking. All identifications here are tentative.

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Genera, Species of Aquarium Interest: (To Do: Need to insert species by genera and images, links per Bklet section BLR)

All told the family Acroporidae contains four extant genera and several hundred species, of which dozens make their way into the aquarium interest.

Genus Acropora, identified readily with their one apical "growing tip", many radial corallites. With a hundred and thirteen scientifically described species of many colony morphologies. These are what most people picture when they hear the word "coral". Most are branched tree-like or interwoven, with fast growing and often differently colored apical corallites (growing tips). These are the mass spawners, with their axial corallites releasing sex cells seasonally. Due to their fast growth (sometimes more than an inch a month), mix of available species and colors, this is a favorite genus of advanced reef aquarists. This genus is divided into fifteen 'groups' on the basis of gross physical appearance (See Fossa & Nilsen, Veron) with some correlation with aquarium survivability.

Branching Acropora, field identified as A. cerealis

And wholesale labeled and cultured as A. cerealis. Commonly called

"Purple Tip Acropora"

Acropora cervicornis, one of two Staghorn Corals of the tropical Western Atlantic. To eight feet in height, branches to more than an inch diameter. Cozumel image.  (An Acropora of the Caribbean, two spp. and a hybrid between them; A. palmata and A. prolifera.)

Acropora caroliniana, Mabul, Malaysia
Acropora echinata, Mabul, Malaysia
Acropora granulosa, Mabul, Saba, Malaysia

Acropora formosa, here are young, open colonies that will become more interwoven with growth. A hardy species sold by wholesalers and culturists everywhere.

Acropora haimei (Milne Edwards and Haime 1860). Colonies of short, upright, tapering branches, with axial corallites which are exsert, tubular and upwardly projecting. Radial corallites similar with sharp-edged lips. Red Sea image.

Acropora hemprichii (Ehrenberg 1834). Irregularly branched with radial corallites as open thickets, large, round, upright, conical. Axial corallites common, prostate, of thick smooth walls. Most are brown to pink in color. Red Sea images.

Acropora humilis (Dana 1846). Finger like colonies whose branches are thick, tapering to a dome. Larger branches intermingled with smaller. Radial corallites of two sizes; larger ones in rows slightly enlarged toward base.   /COTW

Characters: Colonies are digitate. Branches are thick, gradually tapering to large dome-shaped axial corallites. Small branchlets or incipient axial corallites usually occur at the base of main branches. Radial corallites are of two sizes, the larger are usually in rows, have thick walls and only increase slightly down the sides of branches.

Colour: Many colours, but most usually cream, brown, purple or blue (which may photograph purple) with blue or cream tips.

Similar Species: Acropora gemmifera, which has small axial corallites and radial corallites increasing in length down branches. See also A. monticulosa and A. torresiana.

Habitat: Exposed upper reef slopes and reef flats.

Abundance: Usually common, and sometimes a dominant species.

Red Sea images. 

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Acropora hyacinthus (Dana 1846). Colonies as wide, flat plates, possibly tiered. Branches fine in low wave action environments, fused in brisk ones. Branchlets are fine, upward facing. Axial corallites not exsert, but distinct; radial corallites are cup-shaped. Red Sea images.  /COTW 

Characters: Colonies are wide flat plates and tables or tiered aggregations of small plates. Branchlets are thin and finely structured except where exposed to wave action, when they become closely fused. Branchlets are fine and upward-projecting. Axial corallites are distinct but not exsert. Radial corallites are cup-shaped and form rosettes.

Colour: Uniform cream, brown, grey or green with or without blue (which may photograph pink) growing margins.

Similar Species: See Acropora cytherea, A. tanegashimensis and A. spicifera.

Habitat: Upper reef slopes and outer reef flats.

Abundance: One of the most abundant corals of exposed outer reef slopes of much of the western Pacific.

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To: Part 2, Part 3

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