The Branching Metallic Green Frogspawn Coral, Euphylia divisa, is a large polyp stony coral species with long, flowing fleshy polyps that extend from a calcified (stony) base. In a moderate water flow, these corals look a bit like a Frogs spawn, which is where they got their common name. The Frogspawn is similar to the hammer coral and the torch coral except that the polyps are branched with round lobes, as can be seen in the images on this page. Frogspawn corals are generally hardy and are a good addition to most reef tanks. They are the perfect blend of stony coral and soft coral, sure to be a pleasant addition to any reef aquascape.
Aggressiveness The Frogspawn coral has potent sweeper tentacles that it will send out to other corals from growing too close and will sting anything within reach with its nematocysts. Because of this, you should take care to ensure that your Frogspawn coral has enough room both now and in the future, once the corals in your tank have begun to fill-in the available space.
In terms of water flow, these corals also prefer a low-to-moderate flow. Too large a flow will cause the polyps to retract, or be damaged and may also encourage sweeper tentacle issues (see below for more information about that).
Since the Frogspawn Coral is found in shallow water regions on the reef it requires moderate lighting levels (from PAR 150-250).T5's, Metal Halides, or LED's can all grow Frogspawn Corals when the proper PAR levels are provided. We recommend a 14-20K color spectrum for best coloration. If it will be exposed to brighter lighting it needs to be acclimated to the high output lights in the tank slowly, as it is not usually exposed to intense lighting in the ocean because of its depth. Start out with low lighting, positioning the polyps to face out (versus upwards) and have it shaded by rock or something within the tank. The lighting can gradually get stronger over time, but make the changes very slowly.
A mature, well-fed live rock/reef environment is what is needed for your Frogspawn Coral, along with some fish for organic matter production, and dissolved organics. As a general rule, caution should be used when mixing leather coral and large polyp stony coral species, including the Frogspawn coral. Large polyp stony corals protect themselves by wielding their sweeper tentacles maliciously. Many of the leather coral species, by comparison produce and release toxic chemicals, called terpenes, into the water to stunt the growth of other species.
Diet and Feeding
It is not necessary to feed a Frogspawn coral, although they are capable of eating fairly large (by coral standards) meaty foods. The fact that they are biologically able to consume rather large, meaty meals, suggests to me that feeding should be strongly encouraged. However, Euphylia glabrescens could be kept successfully in a reef tank without any feeding at all, as long as adequate lighting is provided, because their symbiotic zooxanthellae will sustain them. If you want to feed, they will eat mysis, fortified brine shrimp, rotifers, Cyclopeeze and other similarly sized meaty foods. Larger pieces than a typical mysis is not digestible, and although the animal "accepts" it, it will regurgitate it up later in the night.
Problems with keeping the Frogspawn coral One of the biggest problems I have seen beginner hobbyists have is failing to account for the calcium demand for these corals. If there is insufficient calcium in your aquarium water, these corals will not be able to make their coral skeleton. You should also never lift a Frogspawn coral out of the water, if you can avoid it. You could tear the polyps, and torn polyps are prone to infection followed by necrosis (a complete deterioration of the tissue).
Reproduction by fragging and budding
Since the Frogspawn coral is a branching stony coral species, it is fairly easy to propagate via fragging. You can cut, saw or snap off a branch and it will grown into an entirely new colony all on its own. A Frogspawn coral frag should command a premium, compared with some of the most commonly available leather coral species, so it is a great coral to grow and trade with other hobbyists.