What The Helio
The Green Long Tentacle Plate Coral (Heliofungia actiniformis) is a very unique critter in the marine aquarium. This stony coral is “free living,” in that the entire coral can (and does) move about for most of its life. As juveniles they are attached to rock or substrate, but break free, leaving a scar on the bottom of the skeleton. After that point, they can “inflate” and “deflate” their tentacles with water, allowing the corals to flip themselves over, stay on top of soft, even muddy substrates, and relocate themselves! It is one of the biggest solitary polyp corals; other examples of solitary polyp corals include Fungia, Cyloceris, Trachyphyllia, Scolymia etc. In wildly oversimplified terms a solitary polyp coral is one that only has one mouth.
Heliofungia is the only species in its genus. It has some traits that seem like it could be grouped with Fungias (and it once was) and some traits that make it seem more like a Euphyllia. In appearance, it often resembles an anemone more than most corals, and interestingly, this similarity is reflected in its care as well. They are photosynthetic but will do much better with supplemental meals. They need gentle, turbulent flow, moderate light, and will relocate themselves if they aren't happy with their placement. Sound familiar? (If you've kept just about any anemone, it should.)
Keeping Long Tentacle Plate Corals is very straightforward. All the aquarium parameters you're used to hearing for reef tanks are appropriate here. The temperature should be in the mid to high 70s, the specific gravity should be around 1.025, nutrient levels should be low (but not zero), pH around 8 and everything should be stable. They can live on a variety of substrates, from refugium mud to sugar sand and even mixed grain aragonite and crushed coral. There isn't really a minimum size of display as long as they can fit on the bottom and extend their polyps, and the water quality is stable, you could keep a Heliofungia in it.
One thing that hobbyists should pay particular attention to when keeping Long Tentacle Plate Corals is tankmates. As was previously referenced, this is a mobile coral, and it does have a relatively potent sting. It can damage other corals and also be damaged by them, if the other corals have aggressive tendencies. Many Heliofungia can be kept together, but they may damage other bottom dwellers like Scolys. Another arena where we recommend some caution is with fish. Many Butterflyfishes will pick at and consume the tentacles of Helios, which usually ends in the demise of the coral. In the wild, this coral is not a natural host for Anemonefish, but in captivity, it isn't uncommon for Clownfish to attempt using Heliofungia as a home. If the coral is very large, and the clowns are very small, this can work out to the benefit of both critters, but if the clowns are too big, they can easily “over love” the coral and irritate it to death. Interestingly, many shrimp in the Periclimenes genus like Pederson's Cleaner will happily live within the tentacles of these corals and this makes for an interesting display.
In regard to lighting and flow, this coral will move around the bottom of the tank until it finds a spot that it likes. Lighting does not need to be overly intense, though if it is kept under low intensity lighting, feeding needs may increase. They are not a good choice for aquariums with intense flow, as their long delicate polyps can be damaged in it, making them prone to infection. Like most corals (especially large polyped ones) we recommend feeding your Heliofungia a minimum of once per week. Feed them a small amount of appropriately sized meaty foods. Foods like mysis can be gently basted directly into their tentacles when the coral is small, and when the coral grows, larger foods like chopped silversides and shrimp can be hand fed to them. Try to size the food to be no longer than ¼ the size of the coral's mouth. Feeding Heliofungia will make them stronger, healthier and more colorful.
Green Long Tentacle Plate Corals are staff favorites here for the lowest level of reef aquariums. They have been popular with coral keeping hobbyists for a long time for all of the reasons laid out above. Few corals can add this much color and movement anywhere in a tank, let alone the sand bed. While they do not respond well to attempts at fragging, if you supply them with their pretty straightforward requirements, and pick good tank mates, Heliofungia actiniformis will give you many years of enjoyment. Now head over to your Local Fish Store and ask about getting one from Quality Marine today!