Beginner marine aquarists may look at coral reef tanks with a bit of envy. After all, it’s well known that corals demand extremely pure water. And that the slightest misstep will result in expensive failure.
But what if there was an inexpensive, beginner friendly coral that grows like a weed? Xenia Coral is fascinating, beautiful, easy to find, and a great introduction into the world of soft coral!
What is Xenia Coral?
Pulsing Xenia Coral. Pom Pom Coral. Pulse Coral. They go by quite a few common names, all of which are very accurate. Xenia Coral are actually a single genus (Xenia sp.) of dozens of different species rather than one specific coral. They all look fairly similar but are different in color and shape.
Most species actively pulse but not all. Xenia Coral typically pulse around 8 times per minute, with variation depending on the health of the coral, flow rate around it, and other factors. Scientists (and aquarists) aren’t 100% sure as to why they do so.
All available evidence suggests that the corals are intentionally creating flow around themselves. This ensures they get a steady supply of dissolved nutrients; quite an active undertaking for what we normally think of as passive, even boring, animals!
Xenia Corals are very polarizing in the marine hobby. Many aquarists consider them easy to the point of being pests. In aquariums with ideal conditions they can grow to cover every square inch of living space.
On the other hand, many advanced reef keepers find them to be extremely challenging to grow and a waste of money. Thankfully, the reasons behind these differing experiences are easy to understand with a bit of discussion on caring for Xenia Coral!
- Common Names: Pulsing Xenia, Pom Pom Coral, Waving Hand Coral, Pulse Coral, Xenia Coral
- Scientific Name: Xenia sp.
- Origin: Red Sea & IndoPacific Ocean
- Height: 3-6 inches, not including the base
- Aquarium Size: Any
- Temperament: Peaceful but aggressive growth in ideal conditions
- Ease of Care: Easy to Difficult
Caring for Xenia Coral
Xenia Coral is actually very easy to care for. Too easy, as you will soon discover…
Aquarium Size
Pulsing Xenia Coral is very adaptable when it comes to aquarium size. You can keep them in anything from a nano reef on up to the largest of display tanks.
When choosing a tank keep in mind that Xenia Coral is almost exclusively photosynthetic. They don’t eat like anemones and many other corals but need access to intense lighting.
So we want shallower tanks over deeper ones. “Long” style tanks like a 20 gallon long are ideal as the depth isn’t so great that lighting gets diminished. Even if you have a deeper tank or substandard lighting you can place the Pulsing Xenia higher up so that it’s constantly well lit.
If your tank is too deep, you’ll see your Xenia struggle to grow or grow lanky in an effort to reach the light. You may see it growing tall and think it’s thriving when in fact it’s actually struggling. The coral may even detach in an effort to reach a better spot.
Lastly, be aware that these corals are incredibly invasive. In the right environment one Pulsing Xenia can multiply in just one year to cover the hard surfaces of a smaller aquarium. Slower growing corals, which is the vast majority of them, can be overwhelmed by a happy Xenia colony.
A larger aquarium is a good idea to give your Xenia Coral space to multiply without smothering other reef organisms. But even so, you’ll need to be very diligent on keeping it contained. A Xenia-only tank may be the best path if you don’t want to constantly maintain it.
Water Quality
You might have been confused by my description on the Ease of Care for Pulsing Xenia Corals as “Easy to Difficult.” In fact, it actually makes sense and here’s why.
As I said before, Xenia Corals are entirely photosynthetic. They rely on the symbiotic zooxanthellae (beneficial single-celled algae) that live in their tissues for nutrients. The coral provides the algae protection and nutrients and the algae provide the coral with food.
Since Xenia Corals don’t require physical foodstuff they need higher levels of dissolved nutrients in the water. These nutrients include nitrate, phosphates, organic molecules, and other agents that are pollutants to most reef keepers.
Most other corals, such as SPS (small polyp stony) corals, require ultra-pure water to thrive. Experienced aquarists therefore often rate Xenia Coral as difficult because they provide them with conditions ideal for other corals. The Xenia Coral then starve because they aren’t getting the nutrients they need in an advanced marine reef tank.
Beginner reef aquarists, on the other hand, often find Xenia Corals to grow explosively because they aren’t as good at keeping the water free of waste products (or nutrients, depending on your view).
It’s possible to strike a balance between cleanliness and health, though. While nitrates and other parameters shouldn’t be at 0ppm for Xenia Coral, a few ppm will allow them to grow without harming other invertebrates.
Ideally, you’ll test as close to 0ppm as possible as we want the Xenia to absorb residual nitrates, phosphates, and organics. Also, if nutrient levels are too high the Xenia is going to grow like a weed, creating more work.
This ability to feed on nitrogenous waste makes Pulsing Xenia one of the best corals for aquariums with high fish loads.
In terms of other parameters Xenia Corals thrive in temperatures between 75-82℉ and a specific gravity (salinity) of 1.023 – 1.025. They also do appreciate slow to moderate current but not strong current.
In fact, it’s theorized that their pulsing motion is meant to create a continuous flow of water around them. Which makes perfect sense considering they feed entirely off of dissolved nutrients and photosynthesis.
Feeding Xenia Coral in a Refugium
One of the best ways to feed Xenia Coral is to keep them in a refugium! A marine refugium is like a protein skimmer and biological filter rolled into one unit. Living organisms like macro algae and gammarus are the main components of the waste breakdown clean up crew.
Refugiums use a pump to draw water into a separate compartment just like a typical filter and include a light to fuel photosynthesis. What better growing environment for Xenia Corals could there be than a box with flow, light, and high levels of nutrients?
As the above video shows, Pulsing Xenia can absolutely thrive in the confines of a refugium. If you decide to go this route, you’ll need to start slowly. Continue to use a protein skimmer on and off while your Xenia colony establishes itself.
You want to ensure that it gets nutrients but doesn’t starve. And you want the water quality to stay good but still be “impure” enough to feed your Xenia Coral. Eventually, the corals in the refugium will reach equilibrium with your aquarium ecosystem.
The Pulsing Xenias may start to crowd out macro algae and other organisms in a small refugium. So you’ll want to aggressively prune them as needed. You can even take extra stalks, attach them to rubble, and resell them to hobbyists for a profit.
Tank Mates for Xenia Coral
Xenia Corals can be kept with a wide array of marine organisms. Any fish that’s reef-safe can live with Xenia Corals. This includes Clownfish.
Xenia Corals aren’t an aggressive species. They don’t sting, release toxins, try to digest or release sweeper tentacles to attack nearby corals. Their mucus isn’t too poisonous to other corals but not exactly harmless.
The main problem is that when given good conditions they spread like wildfire. Xenia Corals can simply grow over and overwhelm just about anything in the tank. Your other corals will be smothered and die from lack of light (and possible irritation from Xenia Coral mucus).
It’s best to keep 4-5 inches of space between them and nearby corals in your tank. This way you can keep the Xenia pruned back and it has space to expand and shift position if necessary. Many successful Pulse Coral keepers also advocate keeping them in a species-only tank so they have all the room they desire.
Alternatively, you can keep Xenia Coral with more aggressive species like Hammer Coral, Torch Coral, and other LPS (large polyp stony) coral types. LPS Corals tend to be more ready to do battle with pushy neighbors. They have sweeping nematocysts (stinging tentacles) and other defenses to keep Xenia Corals at bay.
Clownfish can make fantastic tank mates for Xenia coral because they will treat them like anemones. While Xenias don’t sting their pulsing arms and thickly bunched growth makes them an excellent substitute for the harder to keep sea anemones.
While there are some easy to keep sea anemones out there, even the easiest prefer much purer water than Xenia Corals do. The Xenia may close up on occasion if the Clownfish starts burrowing in too aggressively. But they cause no harm to the coral and are fascinating to watch!
Good Tank Mates for Xenia Corals:
- Clownfish, Tangs, Basslets, and other Reef-safe Fish
- Aggressive Corals (Hammer, Torch, and other LPS Coral)
- Shrimp, Snails, Crabs, and other Invertebrates
Poor Tank Mates for Xenia Corals:
- Peaceful, slow growing Corals
- Sponges, Feather Duster Worms, Clams, and other sessile invertebrates (may get smothered)
Watch out for Xanthid Crabs as well. Also known as Xenia Crabs, they are sometimes found embedded among the polyps of the Pulse Coral. The crabs are small and usually camouflaged perfectly to match their coral host.
As any reef keeper knows, free invertebrate hitchhikers are usually a mixed blessing. Xenia Crabs are parasitic. They live within the coral and nibble away at it periodically. This can stress the coral quite a bit over time.
In an aquarium with good growing conditions the coral’s reproduction should match or outpace the crab’s consumption. But if you don’t have enough light or nutrients the crab’s grazing will contribute to the death of your Xenia. You can either remove the crab or keep it if your Xenia Coral looks healthy enough.
Propagating Xenia Coral
Once you have a healthy Xenia Coral then you’ll almost certainly see them reproduce on their own. Xenia Coral can reproduce by pedal fission where the coral will drop a piece of its “foot.” This piece can then grow into a clone of the parent.
If you aren’t feeling patient you can snip pieces of the coral off to propagate yourself. A healthy Xenia Coral can withstand some cutting. A coral fragging kit is essential as you want precise, razor sharp tools to ensure the coral regrows as quickly as possible.
Simply snip a section of interconnected branches from the body of a mature, thriving Xenia coral. You can attach them to a piece of rubble and use a piece of mesh to tie them down and hold them in place. The Xenia Coral will attach itself to the rubble piece within days and then start growing through the mesh. These young frags can then be sold or placed in a tank to grow out.
Something to watch out for even in a healthy colony is the dreaded Xenia Crash. For reasons not entirely understood (something you’ll hear often when discussing coral) Xenia Coral will die en masse. It’s actually tied to normal coral reproduction, not poor water quality.
In nature a Xenia Crash is thought to be linked to lunar cycles like other coral breeding events. In the home aquarium the corals are relying on other signals but they still manage to coordinate simultaneous die-offs.
When this happens an entire Xenia colony will melt, which has drastic effects on water quality. Assuming this doesn’t cause the rest of your tank to crash, you’ll then see buds left behind. These will soon grow into new Xenia Corals that will re-establish themselves.
The potential of a Xenia Crash adds one last frustrating layer to these strange easy yet difficult to grow corals. This is yet another reason to keep them well under control.
