The branching bubble coral, Plerogyra simplex, is a little known species of LPS coral which deserves to have a moment in the spotlight. There are many different types of bubble corals, and several different species, but the branching species has always fascinated us for having a radically different growth form from the usual large single mass of vesicles that are bubble corals.
As a group, the bubble corals are appreciated as individual specimens, but no hobbyists really go out of their way to learn more about and understand the diversity of species with bubble-shaped tissue. The various species of bubble corals include large bubbles, medium sized bubbles, pearl shaped bubbles and ‘octobubble’ with slightly misshapen vesicles.
But of all these species, Plerogyra simplex is the most distinct for having a deliberately branching growth shape, allowing it to grow into very large colonies, and making it the best candidate of bubble coral to propagate. Branching bubble corals are widespread in the Indo-Pacific being particularly common in some coral-collecting areas, but they are much less well represented in the aquarium hobby.
We get that when it comes to a Bubble Coral with a capital ‘B’, aquarists want the big showy specimen with huge bubbles with green, swirly or striped cat’s eye colors. Normal bubble corals are super hardy and grow very very large, but the colonial nature and smaller vesicles of branching bubble coral makes it a much more suitable choice for home and nano reef tanks.
We’ve seen plenty of small colonies of branching bubble corals before, both in the wild and in aquariums, but we got to see a nice, sprawling colony of Plerogyra simplex in an ideal habitat in Tulamben, Bali. It was not far from where we sighted that exceptional blue squamosa clam, in deeper water further down the slope we came across this large colony of branching bubble coral that was bigger than any we’ve ever seen before.
In this environment, the huge colony of branching bubble coral was establishing itself much like a branching Euphyllia coral would. Seeing how unique and easily fragged Plerogyra simplex could be, it’s peculiar how rare it is to see a branching bubble coral in home aquariums.
Although we grow lots of branching hammer, torch and frogspawn corals in our reef tanks, for some reason the very similar branching bubble coral is notably absent. All it would take for the hobby to get on board with branching bubble corals in aquariums is for someone to find and propagate a green form of P. simplex but alas, we’ve so far only ever seen it in shades of pinkish brown.