Palythoa Vs Zoanthids: What’s The Difference?

When searching for more mesmerizing corals to add to your saltwater aquarium, you probably came across corals called Zoanthids and Palythoas – a large group of corals that are fairly inexpensive and easy to keep, making them great for both beginners and experienced coral collectors.

Even though they have different names, they may appear exactly the same to you, especially if you are just getting started in the aquarium hobbyist world. 

Differentiating Palythoa and Zoanthid Corals is no walk in the park…

So, whether you may be thinking how to tell two corals that look VERY similar apart, or are curious how corals are identified into different groups, by the end of reading this, you should have a clearer idea which coral you have!

What Makes These Corals So Difficult To Identify?

Now, over the years I have come across many Palythoa (Paly) and Zoanthid (Zoa) Corals, and in the past, I could fairly easily differentiate the two. However, with more color morphs popping up in the coral trade, the more difficult it is to tell them apart. 

Taxonomy is a study you should have covered in biology class. However, for those that were not paying attention, it is a study of classification that has been evolving for centuries. If I said “Carl Linnaeus” are any bells ringing yet? 

If not, you need to know that taxonomy is important to understand how organisms are connected, and while we have spent many years studying humans and our links to primates, coral taxonomy is a rather “gray area”, seriously lacking in research. 

Marine biologists are working with taxonomists to differentiate genomes between Palys and Zoas, and while it may be simple for these experts, when it comes down to the average hobbyist, telling the difference scientifically between the two is proven difficult when we do not have the skills or equipment. 

Without the extensive knowledge marine biologists and taxonomists have, when it comes to identifying your coral, there is no guarantee you will be 100% correct. But, do not lose all hope yet, there are still some major differences that you can notice that will help you get a rough idea whether you’re looking at a Paly or a Zoa Coral. 

Palys Vs Zoas

Telling apart Palythoa and Zoanthids is quite difficult unless you have studied coral biology and know what to look for under a microscope. However, below are some differences that even a beginner hobbyist can use to identify, all that is needed is a little patience and a careful eye!

Color

The first thing we usually look for in corals is their amazing colors! This is one of the ways we can tell the difference between Palys and Zoas. 

Palythoas typically come in slightly duller colors than Zoas. Zoanthids come in vibrant colors including reds, oranges, blues, and greens compared to Palys, which come in more “earthy” tones like brown, cream, or green with contrasting colors between their oral disc and tentacles. 

Tentacles

The size of your coral’s tentacles is another good indication to tell the difference if you are looking at a Paly or Zoa. When you get a chance, take a close look at the tentacles that gracefully decorate your coral’s polyps. 

If you notice your coral has fairly small and short tentacles, you are likely looking at a Zoa as Palys typically have longer and larger tentacles. 

Oral Disc

The next stage in identification would be to look at the oral disc – the middle part of your coral’s polyp. 

A Zoanthid’s oral disc appears more round because of a muscle called the sphincter. This specialized muscle opens and closes, acting both as a mouth and an anus. 

Now when we take a good look at a Palythoa Coal, it seems to be missing the sphincter, therefore their oral disc looks more like a slit than a ring.  

This is why you may have heard your reefer buddies saying Palys have a slit mouth and Zoas have a round-shaped mouth. 

Skin

Visual differences such as your coral’s skin can also help you identify whether your coral is a Paly or a Zoa. 

Palythoa corals are pretty cool, as they are known to absorb the substrate inside your aquarium to allow more protection. If you look close enough, you may see small pieces of sand, crushed shells, or whatever you use as a substrate decorating the surface of your coral’s skin. This type of behavior gives Palys a more rough and thick appearance than Zoas. But, before we go any further, I have a word of warning – if you touch your coral to determine its thickness, always wear gloves because many Paly and Zoa corals contain palytoxin which is very dangerous if it gets into your bloodstream. 

Now, if you don’t notice a rough sandy texture, it is likely you have a Zoanthid, as they cannot absorb the surrounding substrate into their skin. This gives Zoas a thinner appearance, and therefore their polyp tissue is more likely to become damaged – so always handle with care and remember to wear gloves!

Growth

How fast Palythoa and Zoanthids grow, is a common question asked, however, the rate of their growth is not what helps you tell them apart. It is usually their growth formations that can aid you in identifying which coral you have. 

Zoanthids and Palythoas both embed their polyps into a mat, but Palys are more likely to grow into a dome-shaped formation, giving a more 3D appearance. 

Behavioral Differences

Visual differences are the easiest method of coral identification, however, you can also look at their behavior – it is easy, but it is a little more time-consuming. 

Next time you feed your coral, take a look at their feeding response. Palythoas can be more aggressive than Zoas, which comes from the Palythoa Corals’ excitement when they are fed, compared to Zoas that are a little more fussy and inactive during dinner time!

Conclusion

Even if you are not a marine scientist, with the above differences, it is an excellent place to start in differentiating if you have a Palythoa or a Zoanthid Coral. 

One thing we do know is that Palythoa and Zoanthids are both a hobbyist’s dream, adding an array of colors to your aquascape, and creating that ultimate mini tropical reef you’ve always wanted!