Coral Profile: The Frogspawn Corals


Pink tip Frogspawn Coral

The species of corals commonly referred to as the frogspawn coral are a popular addition to most mixed reef aquariums. They are defined in the hobby by their distinctive branching tentacle shape and coloration. Frogspawn coral are a moderately easy way to add color and movement to your reef aquarium.


Nomenclature

The frogspawn coral is a prime example of the importance of scientific names. In the aquarium hobby, this coral is referred to as the frogspawn, wall, grape, octopus, and honey coral. The most frequently used common name however, is frogspawn.


Branching type frogspawn coral

The frogspawn comes in two forms. One is the branching type, which has its own coralites (individual calcium skeleton cells). The other form is the wall type. These are actually two different species of frogspawn. They were first described as Euphyllia divisa (wall type) and Euphyllia paradivisa (branching type) by Veron and Pichon in 1979, and 1990 respectively.

Branching Type Frogspawn

In 2017, Euphyllia divisa and Euphyllia paradivisa were reclassified as Fimbriaphyllia divisa (wall type) and Fimbriaphyllia paradivisa (branching type). Before 2017, Fimbriaphyllia was a subgenus within the Euphyllia genus. Due to significant biological differences, Fimbriaphyllia was promoted to genus, and the frogspawn was reclassified with it.


So as it stands today, when you purchase a branching type frogspawn at the fish store, you are buying a Fimbriaphyllia paradivisa, and when you buy a wall type frogspawn, your getting a Fimbriaphyllia divisa. For the purposes of this article, we’ll continue to use the common name frogspawn, as it covers both species.


Description

Branching type frogspawn corals

The frogspawn coral is named as such due to its similar appearance to a mass of frog eggs. The individual coral polyps have branching tentacles with nodules on the end. Their coloration varies from gold-brown to green to pink-purple with either whitish, pink-purple, or green nodule tips.


Like most calcified coral colonies, frogspawn have an indeterminate lifespan. This means the colony and its genetic lineage can live for hundreds of years.


They also have indeterminate growth, meaning they keep growing to the size their environment allows. There are no internal biological mechanisms to limit growth, like with humans and many other animals.


Distribution

Frogspawn coral distribution

Frogspawn is distributed throughout the Indo-Pacific Islands, the Philippines, the Solomon Islands, the American Samoa, and the Red Sea. It is classified as vulnerable under the International Union for Conservation of Nature’s (IUCN) threatened species list.


As hobbyists, it is important to only purchase corals that have been grown in captivity. This becomes easier every year, and you can do your part as well. This article explains how to grow-out and fragment your own coral colonies.


Habitat

Frogspawn is found in habitats protected from harsh surface wave action. It prefers fringing reef crests, mid-slope terraces, and lagoons. Frogspawn lives in depths between 6 and 82 feet.


Aquarium Habitat

Frogspawn prefer mid to top level placement in the aquarium with moderate flow and lighting. They should move and pulse in the water flow, but not “beat” or “wrap” against the walls of their skeleton; this can cause polyp tissue damage.


Frogspawn is a fairly aggressive species and should be placed far enough away from neighbors so as not to sting them. At night, frogspawn can release its stinging nematocyst cells (sweeper tentacles) up to 6 inches. Any corals within that distance can be stung and their polyp tissue damaged.


Aquarium Water Parameters

pH

8.1 - 8.4

Salinity

1.022 - 1.025 sg

Alkalinty

7.8 - 12 dKH

Calcium

400 - 480 ppm

Magnesium

1300 - 1400 ppm

Temperature

74 - 77 degrees Fahrenheit

Water Flow

Moderate

Preferred Lighting

Moderate - High

Maximum Size

Indeterminate

Life Span

Hundreds of years

Tank Size

20+ U.S. Gallons

Disposition

Aggressive to corals outside of Euphyllidae family.

Diet

Frogspawn, like nearly all corals, have symbiotic algae in their cells called zooxanthellae. These algae photosynthesize within the coral polyps and provide important sugars for the coral’s energy and growth requirements. They are also responsible for most of the color and fluorescence of the coral.


While providing light for the zooxanthellae is important for coral health, corals are still animals, with mouths and stomachs. The additional feeding of animal or plant matter (depending on the type of coral) is crucial to coral health and growth.


Frogspawn will benefit from target, or spot feeding. This is a method where food such as small shrimp, or mixes of planktonic micro animals are applied directly to open coral polyp mouths. They should be fed at dawn or dusk, when their feeding tentacles (nematocysts) are visible. They can be fed this way multiple times a week. For specifics, check out this article on coral feeding.


Acclimating New Corals

Frogspawn can succumb to several common ailments. Most are initially caused by stress. To prevent these ailments, the best practice is to dip and acclimate your corals when adding them to your aquarium.


Dipping corals removes unwanted parasites, bacteria, and protozoans which can cause damage to your new and already established corals.


Acclimating new corals lowers the stress put upon them and decreases the chances of them succumbing to an infection. Acclimation usually includes a 30 - 45 minute drip of your aquarium water into the bag water your coral came in. Check out this article on drip acclimation for how to drip acclimate successfully.


Acclimation also includes keeping flow and light intensity turned down for several days after adding the coral to your aquarium. Slowly bring the intensities back to normal over the course of a week. If your coral reacts poorly to the lighting or flow (polyps recede, coral loses color), then find a new placement for them.


Frogspawn Ailments

Frogspawn can succumb to polyp nipping, handling damage, brown jelly infections, bleaching, and polyps receding.


Polyp nipping can only be prevented by excluding non-reef-safe fish and invertebrates from your reef aquarium. Handling damage can be prevented by proper transport, dipping, and only handling corals by their base or skeleton.


Brown jelly infections are a response to stress where certain protozoans are allowed to enter the coral polyps, causing them to melt and produce a brown, jelly-like substance. Dipping infected corals may help, but this condition is pretty severe.


Bleaching is a loss of color, and like receding polyps is a sign of stress. This stress can be brought on by poor water quality, an infection, imbalanced water chemistry, improper lighting or flow, polyp nipping, or handling damage.


Experiment

In my experience, most people treat corals as if they are hardier than fish. Corals are often not acclimated properly and added to unestablished reef tanks too quickly. The key to coral health, especially your new frogspawn, is to properly acclimate your new specimens by drip acclimation and lower light and flow intensity for the first few days, and by observing your coral for signs of stress. If you see any of the above mentioned bleaching, or receding polyps, immediately test your water chemistry for elevated nutrients or an imbalanced calcium, magnesium, and alkalinity ratio. Then check your flow and lighting to make sure they are not too strong. Finally, watch your fish and invertebrates during the day and for at least a short period at night, to make sure they are not damaging your coral's tissues.



Literature Cited


Hoeksema, B. W.; Cairns, S. (2022). World List of Scleractinia. Fimbriaphyllia divisa (Veron & Pichon, 1980). Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=1048074 on 2022-06-13


NOAA Fisheries. Species Directory. https://www.fisheries.noaa.gov/species/euphyllia-paradivisa-coral. Accessed 6/13/22.


Turak, E., Sheppard, C. & Wood, E. 2008. Euphyllia paradivisa. The IUCN Red List of Threatened Species 2008: e.T133057A3586802. https://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T133057A3586802.en. Accessed on 13 June 2022.


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