Everything You Need To Know About Zoanthids

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Whether you’re new to aquarium keeping or highly experienced, incorporating corals is a beautiful and ecologically smart way to keep your tank looking gorgeous.

As such, have you thought about using zoanthids to brighten up your aquarium? Coral is difficult to properly care for, even if you’re highly experienced.

how to make a zoa garden

However, you’ll be happy to learn this unique species is well suited to beginners, so long as you have the right know-how.

Are zoanthids the delightful addition your tank needs? Let’s take a look at everything you need to know ahead of time.

What Are Zoanthids?

Zoanthids, more commonly referred to as zoas, are officially categorized as cnidarians and are typically referred to as colonial anemones by scientific communities.

You may be surprised to know that the zoanthid coral is not actually coral at all – even if they’re popularly referred to as such.

Because of this, they are often confused with sponges, ascidians, sea anemones, and other blob-like fish species, making zoanthid identification somewhat tricky.

Build

Zoanthids do not grow hard skeletons like most corals, so you will find that their tissue is leathery to the touch.

Their polyps will form a cylindrical body column that looks like a tube with a flat circular disk at the top. Stemming off this disk are small tentacles that are often distributed in two rows that rest close together.

Colors

They grow in a wide variety of sizes and colors.

Typically, they sport their colors in the center of the disk, which then turns into darker colors towards its tentacles.

Habitat

They are common in pretty much every type of marine environment imaginable and are often found in both shallow reefs and in the deepest depths of the sea.

They are not restricted to tropical reef environments either, making their versatility desirable to novice reef keepers.

how to feed zoanthids

Toxicity

Some zoa coral contains the highly toxic substance called palytoxin, which is one of the most toxic organic substances in the world.

There is still some debate among marine experts over the exact concentration of this toxin in these animals, but even the small quantities can prove fatal, should it be ingested or enter the bloodstream.

If you immediately inject vasodilators into the ventricle of your heart, however, this will work as a sufficient antidote.

Are They Dangerous?

Many studies offer conflicting information about the potential dangers of handling a zoa reef tank.

The general consensus among aquarium enthusiasts and marine experts is that a human would need to ingest palytoxin from zoanthids in sufficient quantities – or brush a recent cut over it – to really see any effects.

Even then, proper handling, propagation, and aquarium maintenance are unlikely to pose any real danger beyond a bad skin reaction where you touched the palytoxin.

Other sources say that palytoxin can still be absorbed through closed skin, and that you still run the risk of acute poisoning from venomous zoanthids in this way.

Palytoxin may also damage the eyes of aquarium enthusiasts who attempt to propagate the coral by cutting it and then being squirted in the eye with the toxin by accident. Both temporary and permanent blindness have been reported in these instances.

Of course, it is always recommended that you wear proper eye protection when cutting your corals. You should also wear the appropriate protective gloves when handling sea invertebrates, especially if you are concerned that your zoanthids will accidentally poison you through your skin while working with them.

Interestingly enough, however, palytoxin is being studied in relation to signaling pathways in skin cancer genesis. This is because, in sub-lethal quantities, palytoxin is a tumor promoter.

Perhaps in the future, we may find that the cure (or at least the prevention) for cancer may lie in these fascinating – yet poisonous – creatures.

Zoanthid Care

Zoas are quite the hardy species and are fairly resistant to shock. Still, you should always keep your water parameters as stable as possible.

When changing out the water in your zoanthid tank, be as careful as you would be with any other fish or coral species.

zoanthid identification

By aquarist.me (Creative Commons Attribution-Share Alike 2.0 licence)

Ideal Settings

Most zoas are often found in high-nitrate canals, harbors, inter-tidal areas, and tropical reefs in nature, so they are fairly tolerant of poor water quality or high levels of nitrates, phosphates, and dissolved organics in your tank.

Though they are used to rougher waters, they will also thrive in tanks that have stable water parameters capable of sustaining other saltwater tank inhabitants.

You will want to keep your zoa reef tank quite warm—around 78 degrees Fahrenheit to be precise.

You will also need to keep an average salinity of roughly 1.026 specific gravity.

The hardness of your water should be kept between 7 to 12, with the pH somewhere between 7.9 and 8.4.

A RO/DI water treatment system combined with a reputable reef salt mix and frequent water changes will keep your water parameters well within these optimal ranges.

Promoting Zoanthid Growth

Zoanthids thrive in low to medium-high flow areas. If the flow area is too high, then the polyps, which are the tiny, soft-bodied organisms on the corals that attach themselves to a rock on the seafloor, will have a difficult time opening.

This can stunt the zoa’s growth and future development. The polyps should be fully opened without appearing strained to let the zoa thrive.

This video goes into more detail on zoanthids care.

Zoa Companions

Some zoa species can live alongside sponges or other invertebrates in a mutually beneficial relationship with one another.

At one point, however, zoanthids were thought to be parasitic to these species – though this is no longer the case. If you keep more specialized species of zoa, then you need to be aware that you must keep their companion alive as well.

As such, you need to research which species of zoanthid will go well with these other species nesting in your tank.

Keep in mind, however, that zoas will compete for space just like other colonial and sessile encrusting invertebrates. They often grow fairly fast and will often overtake their neighbors if given the opportunity.

They will often overcrowd other cnidarians as well, so it’s best to keep them isolated on their own pieces of rock amidst some soft coral sand.

Bad Tankmates

Do not place your zoanthids next to your corallimorphs (otherwise known as the mushroom anemone), because your zoanthids will almost always lose their territory to it.

If you must grow these species in the same tank, you should place them a good distance away from each other.

They will also be smothered by filamentous algae, so be sure to remove it from your tank.

Good Tankmates

Zoanthids can be kept with other types of fish as well, but there are some fish species that will dine on your precious corals.

Species like the raccoon butterflyfish, chaetodon lunula, many filefish (monacanthidae), and sharp-nosed puffers (tetraodontidae) are just a few examples.

zoanthid tank

How to Make a Zoa Garden

The Right Materials

Zoanthids are colonial anemones, meaning that you will need to provide them with hard surfaces to encrust over. Surfaces like live rock, regular rock, dead corals, or pieces of porous ceramic will do the trick.

Also be sure to surround this surface with other small materials, like sand. This is because, unlike other colonizing anthozoans or soft corals, zoas create their structure out of these materials to better strengthen their bond and sturdiness to environmental influences.

The Right Flow Rates

Though zoas grown in your tank should not be exposed to high flow-areas to ensure steady growth, zoas in nature are often exposed to strong waves and thus grow shorter and more spread out.

Your zoa garden may look this way if left in a high flow area. Zoanthids living in calmer waters, however, tend to have taller bodies and longer tentacles.

Cuttings

Zoa colonies are made of individual polyps that join together to work as a community. So, in actuality, your zoa may look like a single coral, but it is built up of many individual polyps housed together on the same organism.

These polyps tend to be on the smaller side (less than one inch at the most), but the colony itself spreads out at an almost alarmingly rapid pace.

Remove it From the Tank

When cutting the sample from your mother colony, you will need to take it out of the tank. To start growing another zoa garden in another tank, you can peel some of the mother colony off with a scalpel.

Keep in mind that this can be a difficult and messy process and that it’s often easier to wait for your zoas to overgrow first.

Properly Protect Yourself

If you do decide to cut it a bit early, make sure you wear a mask and protective gloves.

A lot of the zoa’s tissue and slime will be released into the air around you as you transport it to another tank, after all.

You do not want to accidentally inhale some palytoxins when creating a new colony elsewhere.

zoa reef tank

By Bernard DUPONT (Creative Commons Attribution-Share Alike 2.0 licence)

Get Enough Polyp Heads

You should cut off a piece of the mat with a good handful of polyps attached.

The number of polyp heads you eventually decide to cut will be related to the size of your source colony, though six to ten is a good starting number for your zoa to grow in another tank.

Rest the Mother

After separating the cut polyps from the mother colony, let your mother colony rest in fresh aquarium water for a while before returning it to your aquarium.

You should also replace your activated carbon to help reduce any stress chemicals your zoanthids might produce.

These secreted chemicals are basically the zoa’s way of discouraging any fish from eating or harming it in any way.

How to Feed Zoanthids

Zoanthids have a photosynthetic partnership with their zooxanthellae.

This means that their cells absorb light energy from the sun and then transform that energy into glucose, or sugar used to help keep them alive and fed.

Keep in mind that, while zoas can get some nutrients in this manner, it cannot be their only means of food.

This means that you need to target feed them. Specifically, you’ll inject coral food directly above them, targeting it just right so it will land in their mouths.

Their polyps will then fold inward and open their mouths to eat it. This is the most popular feeding method, but you can also choose to simply pour the recommended amount of food directly in front of the powerhead at the same time of day, every day.

Zoas will then excrete a dark brown substance around them the next day or two. This substance is their fecal matter, which your filter should clear out.

Many people confuse their presence with brown jelly disease. If you are concerned that your zoas have contracted this disease, please see a veterinarian that specializes in the care of this species.

If you find your zoanthids refuse to eat the food you give it, you may need to change its diet.

There are plenty of quality food options on the market, but Red Sea Reef Energy A, ​Red Sea Reef Energy B, Polyp Labs Reef-Roids, Brightwell Aquatics Reef Blizzard-S, and the Coral Frenzy “The Ultimate Coral Food” are all excellent brands and choices for your zoa garden.

zoanthids

How Do Zoanthids Reproduce?

Zoas are asexual beings, meaning their offspring arises directly from themselves in a near-direct copy.

Interestingly, the offspring do not float away to start their own colonies, but instead remain connected to the original polyp for the remainder of their life.

LED Lighting for Zoanthids

The majority of zoanthids have symbiotic photosynthetic zooxanthellae and should thus be kept in moderate aquarium lighting.

Some of the more brightly colored variants will tolerate intense lighting from metal halide or newer generation LED lights if acclimated properly, but it is always a good idea to check your zoa species’ preferred lighting environments beforehand.

Here’s a video showing more about keeping zoanthids.

Conclusion

Reef keeping may seem like a daunting hobby for a novice, but it’s not as difficult as you’d expect.

Zoanthids are a great start to reef keeping, and their easy upkeep might inspire you to grow other types of corals and anemones in your tank!


What’s your favorite thing about zoanthids?

Staff Writer
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