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Proper Bubble Coral Care can be a little more complicated than other types of corals. They require specific lighting and water parameters to thrive, so it’s important that you take the time to learn what they need before adding them to your tank! This guide will walk you through all the steps for setting up a bubble coral system and caring for these delicate creatures. Let’s get started!
A Quick Overview On The Bubble Coral
|Scientific Name||Plerogyra spp. and Physogyra spp.|
|Common Names||Bubble coral, grape coral, pearl coral|
|Origin||Country – Widely found throughout the Indo-Pacific and the Pacific Ocean (most colonies are imported from Indonesia)|
|Common Colors||Greens, whites, yellows, pinks|
|Lighting||Low-Moderate (50-150 PAR)|
|Tank Placement||Bottom, Middle, Top|
|Flow Rate||Low – Moderate|
|Temperature Range||76-82 degrees F|
|pH Range||8.0 – 8.4|
|Salinity||1.025 or 35 PPT|
|Alkalinity||8 – 12 dKH|
|Calcium Level||350 – 450 PPM|
|Magnesium Level||1250 – 1350 PPM|
|Propagation||Cutting/Fragging (Expert Only)|
Origins And Habitat
Bubble corals come from a wide range of environments. They have been found in dark and turbid waters as well as bright and clear seas.
Bubbles are largely found throughout the Indo-Pacific and the Pacific Ocean, but most available colonies in the hobby originate from Indonesia specifically; more Australian colonies have entered the trade due to difficult propagation and trading bans on coral.
These corals are commonly known as the bubble coral, grape coral, or pearl coral due to their appearance. Though they have previously been categorized as a member of the Euphylliidae family, their exact taxonomic categorization is largely up for debate and still unknown.
The common name ‘bubble coral’ is actually used to describe two different genera, Plerogyra and Physogyra. The difference between these two genera is that Plerogyra spp. usually have larger bubbles and a blade-like skeleton while Physogyra spp. have smaller bubbles with a flatter skeleton; Physogyra spp. are often referred to as pearl bubbles1.
Some of the most common species to come across are Plerogyra sinuosa and Physogyra lichtensteinii. Luckily, the care requirements for these two genera do not differ.
In the aquarium hobby, these corals may be further named according to their area of collection. For example, you may come across ‘Aussie bubble corals’, ‘Indo bubble corals’, ‘Marshall Island bubble corals’, or wherever else they might have been collected from; these names may even be carried over for those corals that have been aquacultured.
Some hobbyists find Aussie bubbles to be more sensitive than Indo bubbles, but this is specific to each tank.
What Do Bubble Corals Look Like?
These corals look exactly how you might imagine them. Bubble corals are large polyp stony corals (LPS) with a calcium carbonate skeleton and round fleshy polyps. They can grow to be several inches across and reach reasonable heights.
There are two main types of bubble coral variety:
- Ones with rounded, grape-shaped bubbles; some of these that have smaller bubbles may also be labeled as ‘pearl’ (Physogyra spp.)
- Ones with irregularly shaped bubbles
No matter what kind of bubble coral you have, your coral should always be fully extended. The level of polyp expansion can correlate to lighting. Low lighting can cause your coral to inflate more in order to optimize photosynthesis and high lighting can cause more compacted bubbles.
Bubble corals have very jagged skeletons which can easily puncture their own bubbles. This can make transporting them very difficult, but not impossible. For as fragile as they are, hobbyists have found them to be incredibly resilient and can come back from near death.
Along with being fully extended, your bubble coral should have bright colors; though they do not come in many different colors, the greens, whites, yellows, and pinks of your coral should be vibrant. Bubble corals have almost transparent flesh, but color should never be entirely absent.
At night, these corals retract their bubbles. They send out long, clear sweeper tentacles that are used for feeding and attacking any corals that get too close; these tentacles do have nematocytes, or stinging cells, which can cause some irritation or inflammation to human skin and even more damage to nearby corals.
During this time, the skeleton will be exposed and you will be able to see how jagged it really is. Remember, this skeleton should never be exposed at any other time.
Placement In The Aquarium
Bubble corals aren’t the most popular coral in the hobby, but they’re one of the most adaptable.
These corals can be placed in nearly all locations of the aquarium as long as adequate acclimation is allowed for and care is given when handling; these corals can be more top-heavy than others, so long-term placement needs to be secured with superglue (cyanoacrylate) or epoxy.
Do Bubble Corals Like High Water Flow?
No, bubble corals do best with low to moderate water flow. Flow should be just enough to keep the bubbles slightly moving – aim for gentle water movement. Anything more than this could damage the coral.
Moderate flow is needed for these corals to remove algae and debris as well as to keep them fed. At night, they use their sweeper tentacles to help catch food that needs to be moved past them with a current.
How Much Light Do Bubble Corals Need?
Naturally, bubble corals are found in a variety of light intensity conditions. They can withstand lower light (50 PAR) on the substrate or be acclimated to the top (150 PAR) of the reef.
Because of how large they can get and how delicate they are if they fall, most hobbyists choose to keep them on or near the substrate. If choosing to keep them on the sand, make sure that the water flow is not pushing granules onto the coral. This can cause irritation which can lead to retraction and infection.
Wherever you choose to place them, they should be secure and away from anything that could rub up against them, like rock, the aquarium glass, or other corals.
Temperament In The Aquarium
Though bubble corals might look harmless, they need to be given their space in the aquarium. Their sweeper tentacles are relatively long and very capable of inflicting a sting on nearby corals.
It can be difficult to judge placement in the aquarium at first as these sweeper tentacles usually only emerge at night. In general, it is best to leave about 5-6 inches of buffer room for your coral to fully expand and extend its tentacles.
It also isn’t uncommon for your bubble coral to change shapes throughout the day. When the lights come on, your bubble may still have its sweeper tentacles out with a lot of exposed flesh. As the day goes on and the light reaches higher intensities, it may form more compact bubbles.
Bubble Coral Care And Maintenance
Bubble corals aren’t the easiest species of LPS, but they don’t require much special care either. As mentioned before, the biggest concern with these corals is transporting them and acclimating them correctly.
Otherwise, they need standard reef conditions and can be kept with hang on the back, canister, or sump filtration. If you start to notice algae growing around the skeleton, it should be carefully removed with a turkey baster or by hand to prevent it from smothering the polyps.
Bubble corals do not need any additional nutrients as long as a quality marine salt mix is being used. The main nutrients these corals need are nitrates, phosphates, calcium, magnesium, and stable alkalinity; contrary to once-popular belief, corals need available nitrates and phosphates for the best health.
Because bubble corals make their own skeletons, they heavily rely on calcium, magnesium, and alkalinity for steady growth. These parameters are usually maintained through regular water changes, though they might need to be dosed if keeping larger colonies of LPS and/or keeping small polyp stony corals (SPS) as well.
Simply track how parameters change in the tank between water changes. This will show how nutrients are being used and recycled throughout the system. If levels fall too much, then it might be time to start dosing; make sure to only dose what is needed.
Unlike other species of LPS, bubble corals appreciate being fed every now and then. They get the majority of their food from the water column, but will usually willingly accept any supplemental feedings.
In fact, these corals can be fed relatively larger pieces of meaty foods like fish, shrimp, and crab in addition to smaller foods like brine shrimp, mysis shrimp, and coral-specific products. A great coral food to try is reef-roids.
Simply place the food near the mouth of the coral and wait for it to start moving it in. Do not overfeed as this can create unnecessary waste and start to stress out your coral in the long run.
Are Bubble Corals Hard To Keep?
Once settled, bubble corals are easy to care for. They’re not as common to come across as some of the other fleshy LPS species, like Euphyllia, but they can be just as eye-catching in a reef tank setup.
In general, these corals can be kept by hobbyists at the beginner, intermediate, and advanced levels. Handle these corals with care and keep the skeleton clean of algae.
What Are Good Tankmates For Bubble Corals?
Bubble corals are one of the most tankmate-friendly coral options available. As long as it’s reef-safe, there’s a good chance it will get along with your bubble.
Again, the main concern you should have is keeping your bubble coral undamaged. Anything with pincers or sharp teeth, like crabs or triggerfish, could easily damage your coral. Otherwise, tangs, gobies, damsels, and wrasses are all possible options.
Unlike other LPS with longer tentacles, clownfish do not host bubble corals nearly as much. Though bubbles don’t bring as much movement to the aquarium as other similar corals, you don’t have to worry about losing your colony to an overly aggressive clownfish.
Fragging Bubble Corals
Fragging bubble corals is usually not recommended for any hobbyist. But if you’re dealing with an overgrown coral, fragging is your only option.
This process can be most likened to fragging a wall hammer coral in terms of difficulty. It is recommended to attempt fragging a bubble coral only if an electric saw is available. Here is a great video by MileHighReefers that shows the fragging process. I’ll provide a summary below.
There are two main ways to frag your bubble coral:
- Just go for it. If choosing this method, first make sure all polyps are closed as much as they can be. Do this by lightly touching the coral, making sure not to cause injury. Next, look for already-defined lines of division; if your bubble coral is branched, divide the branches. It is not recommended to cut through the mouth or the flesh unless highly experienced.
- Have some patience. This method takes a little more time but tends to have higher success rates, especially if needing to split a large polyp. First, use a rubber band to divide the polyp; you want to force the coral to separate into two. From here, you will have a defined line that can be cut with a saw or, if done carefully, a Dremel tool.
Both of these methods carry high failure rates, though bubble corals are known for bouncing back pretty quickly if something goes wrong.
Why Is Your Bubble Coral Dying?
There are three main reasons your bubble coral might be dying: water flow, injury, or water parameters.
Bubble corals need some flow to deliver food and to keep them clean, but anything more than enough will damage their delicate flesh. If you notice your coral start to close up or recede from the base, check how much direct flow it is receiving and move accordingly.
Injury and infection are the biggest killers for bubble corals and often happens during transportation. When purchasing a coral, but sure that it is fully extended and shows good coloration. Make sure to handle the coral from the base to prevent any further stress or injury; use a coral dip or iodine to facilitate healing. Brown jelly infections are also another common issue with bubble corals.
Unfavorable aquarium water parameters, including lighting conditions, can also cause your coral to die back. Usually, other corals in the tank will also show signs of poor water quality, but LPS can recede very quickly once started. If you recently moved your coral to a higher spot in the tank and it is failing to extend, then you might not have allowed enough time for acclimation.
Bubble corals are relatively easy to care for, but fragging and any excessive handling can cause problems. They don’t come in many colors, but their inflated appearance and full expansion bring life to the middle and lower regions of the tank. With some acclimation, they can even be moved to the top of the reef!