True soft corals are octocorrillians with 8 tentacles on each polyp

Soft Corals: How to care for soft corals in a saltwater aquarium

The term soft coral is used broadly and relatively unscientifically (is that even a word?) to lump a bunch of related and unrelated coral species into a simple bucket, defined primarily by what they are:

  • Soft, with the absence of a major stony external skeleton

And what they are not

  • They are not false corals, like the mushrooms or zoanthids).

The reason any of this is important and worth reading about is that many of these amazing animals (yes, they are animals), are some of the most popular, readily available, and easiest to care for aquarium corals you will find in this hobby. But the taxonomy and proper categorization only really appeal to taxonomists. We care about caring for them in our reef tanks, so let’s dive in to learn more about how to care for the soft corals in a saltwater aquarium.

Table of contents

If you have a specific question, you can use the Table of Contents below to jump right to it or read the rest of the article.

What is the difference between soft coral and hard (stony) coral?

Hard corals, like LPS and SPS (which stands for Large Polyp Stony and Small Polyp Stony), have a substantial external skeleton made of calcium carbonate.

Soft corals, by comparison, have very large, soft, fleshy polyps with tiny pieces of calcium carbonate skeleton included in their tissue. These tiny pieces of the skeleton, called sclerites, look like little crescent moons or even fingernail clippings (gross!).

If you look closely, you can sometimes see these sclerites embedded in the tissue of certain corals. Take a look at this carnation soft coral below.

close up of a carnation soft coral where you can see the white sclerites embedded in the translucent skin near the red polyps

See those white striations in the skin of this carnation soft coral? Those are sclerites, the not-so-stony skeleton typical of a soft coral. They are harder to see when the tissue is not transparent, but they are present in all of them.

Those white lines that look like striations or maybe even worms are actually bony shards made from calcium carbonate, the same material that makes up the stony skeleton of LPS and SPS coral species. The absence of that more formidable stony structure is one of the important characteristics that define this gang of corals.

soft coral vs. stony

What else makes a true soft coral species?

As mentioned above, these colonial animals lack the calcium carbonate skeleton that is present in Large Polyp Stony and Small Polyp Stony corals. But to differentiate them further from the other non-stony sub-classes (Mushrooms and Zoanthids), we have to look at the individual polyps.  The true soft corals belong to the Octocorillia sub-class, which is a term used to describe the corals that are radially symmetrical divisible by 8….er…what? Ok, picture an old school clock with numbers from 1-12…roughly speaking that’s radially symmetrical as divided by 12…now imagine that clock only had hours 1-8, evenly spaced around the clock. The polyps of octocorillians have 8 tentacles. Go ahead, count them.

True soft corals are octocorrillians with 8 tentacles on each polyp

See how each polyp has 8 tentacles on it? That’s why they are classified as Octocorrilians

Zoanthids, by comparison, belong to the subclass Hexacorallia (radially symmetrical but in six symmetrical parts vs. 8) and have a different body structure than the true soft corals–and Mushroom anemones belong to the Corallimorphia subclass, which represents a group of animals with a district morphology from the rest. 

How are Soft Corals different from mushroom corals and zoanthid corals?

Unlike zoanthids and mushroom corals, these are considered to be “true” corals and not colonial anemones or false corals. That doesn’t really mean all that much for the average hobbyist other than to provide some specificity about what we mean when we use the term.

Being true corals, these animals do have some bony elements (sclerites) and they exist as a colony of cooperative polyps that exist as part of a greater structure–compare with zoanthid and mushroom anemones where the comparatively larger polyps are each an individual organism

soft coral vs. zoanthid vs. mushroom

 

Soft coral types

As mentioned earlier in this article, the descriptor, this term is used to categorize a large group of diverse animals.

The most common soft coral types are:

  1. Clavularia
  2. Pachyclavularia
  3. Alcyonium
  4. Cladiella
  5. Lobophytum
  6. Sarcophytum
  7. Sinularia
  8. Capnella
  9. Dendronepthya
  10. Nepthea
  11. Anthelia
  12. Xenia
Dendronephthya hemprichi soft coral at Gilli Lawa Laut

Don’t be allured by this Carnation beauty, they are hard to care for

Soft Coral care

It is a bit tricky (or imprecise) to try and provide care instructions for a grouping of corals as large and diverse as this. But what I will do here is try to focus on the most commonly available varieties.

They are so popular because many of the species are considered beginner corals. What makes a beginner coral? They are hardy, which means they grow well, they are tolerant of aquarium conditions, perhaps a bit forgiving of minor fluctuations in water quality, and only require a moderate amount of light and water flow.

That pretty much describes the cabbage leather, toadstool, devil’s hand, finger leathers, pulsing xenia, Capella, colt corals, and other similar corals. Standard reef aquarium water parameters will grow these corals well.

How to grow soft coral faster

The key to boosting the growth of your soft coral is to (gradually) increase the quality of light (meaning give it more PAR or a higher value of PAR) and to feed your tank a few times a week. I’ve fed my tanks with rotifers, and baby brine shrimp, (which in turn were fed nutritious phytoplankton, like above), as well as freeze-dried cyclops, Reef Roids, and even just blast thawed frozen foods in the powerheads to make a variety of food sizes available.

Testing and water chemistry

testingTo keep soft corals, you will want to regularly test for nitrates, pH, and salinity. While setting up your tank, you will want to track ammonia and nitrite, in addition to the water parameters listed above. Every now and then you will want to confirm that the temperature is stable, somewhere in the neighborhood of ~78 degrees Fahrenheit and that specific gravity is about 1.025 and pH is hopefully around 8.2. 

You shouldn’t have too many problems keeping water parameters around these levels, as long as you use a high-quality salt mix.

Dosing supplements

toadstool leather coral is a soft coral speciesYou probably won’t have to manage complex dosing of supplements if you want to keep soft corals. If you are having trouble keeping calcium and alkalinity high, your tank may benefit from the addition of a 2-part additive, but for the most part, I have soft corals for years without any additional dosing. I just do water changes with Instant Ocean.

Feeding

Corals are animals. Animals like to eat. In addition to providing a good source of reef-building aquarium light, you may also want to feed your corals.

While there is a common belief that soft corals do not require food, that is actually a myth and is quite untrue (Borneman 2001).

While the polyps of your average soft coral species might not have stinging nematocysts, or even the same dramatically visible capture-response that you might see in some other SPS coral species, that doesn’t mean they don’t eat.

Cabbage leather corals and some others have polyps that are capable of capturing and ingesting prey. If the corals you have capture prey, it’s typically a good thing to feed them. A stand-out exception to this rule is with the non-photosynthetic soft corals, like the carnation, which is actually incapable of sustaining itself with photosynthesis.

These corals require regular feeding to survive and are actually not recommended for the beginner aquarist. The key to feeding any coral species is to provide it with food that is the right particle size. Many soft coral species will absorb nutrients right from the water, and others may feed on nanoplankton or bacterioplankton.

If the feeding habits of the coral you’re interested in are not well described, I encourage you to try different feeding regimens and share your results (here or with others).

Check out this comparison between Julian’s Thing and the Sea Squirt to see which tool is best for spot feeding your corals. 

Fragging

Fragging soft corals is a fairly straightforward exercise. You want to cut off a piece and attach it to a piece of live rock or a frag plug. If you are trying to frag one of the encrusting species (like green star polyps), creating soft coral frags is even easier, because the GSP will just encrust any adjacent rock in reach. All you will need to do is separate the new rock colony from the parent.

Cutting soft corals is easy, you just use a razor blade or a sharp set of scissors.

How to attach frags to live rock

Attaching leather can be challenging because they typically are not able to be glued into place. Soft corals are slippery, slimy, and (believe it or not) wiggly. Since many of these fleshy animals are escape artists of the aquarium world, you can use any of the following methods to attach them to live rock (or a plug):

  • Plastic container and mesh
  • Rubber band
  • Toothpick method

to attach them.

rubber band and toothpick methods of attaching frags

The rubber band method (left) and toothpick method (right) are two great ways of attaching slimy, slippery soft corals to an irregularly shaped substrate like live rock rubble

You can find step-by-step instructions for all of these in the book, How to Frag Corals .

Where to buy

The best value for the money can usually be found by buying frags from a fellow hobbyist in your area. Many of the species commonly kept in the hobby can be fragged easily. So your best bet at getting a hardy, inexpensive specimen that is used to living in an aquarium is to get a piece that is doing well in someone else’s aquarium.

After that, the next best option is to get an aquacultured specimen online or at your local fish store. The term “aquacultured” means that the coral was grown (farmed) in captivity and is also likely to adjust better to aquarium conditions in your home than a wild-caught one.

How to care for each of the most popular types

To learn more about how to care fore each of the most popular soft coral types, check out these individual pages:

Best Soft corals for beginners

The 3 best saltwater coral species for beginners are:

  • Green star polyps (this soft coral looks like grass)
  • Toadstool
  • Kenya tree (also sometimes called colt)

I have kept those three more than any other coral type, over the years, because they’re awesome, easy to care for, and easy to propagate.

Written by Albert B. Ulrich III–author of The Reef Aquarium Series of books:  The New Saltwater Aquarium Guide, How to Frag Corals, 107 Tips for the Marine Reef Aquarium, and The Reef Journal.

Learn more by watching this video:

What soft coral species do you have in your tank? Please leave a comment below and let us know what you think of these softies.

References

Borneman, Eric H. Aquarium Corals. Microcosm Ltd; 1st Printing Edition (March 1, 2001)

Ulrich III, Albert B. How to Frag Corals: Step-by-step guide to coral propagation and filling your frag tank with thriving polyps.www.SaltwaterAquariumBlog.com (January 20, 2015).

Ulrich III, Albert B. The New Saltwater Aquarium Guide.www.SaltwaterAquariumBlog.com (April 8, 2014)

 

Comments

  1. I enjoyed reading this article as always, your have such great information in a hobby that has so many different beliefs on what and how to do things. I currently do not have a reef tank but hope to some day start one back up again. Thank you for sharing your knowledge and keep the articles coming. When I did have my reef tank I had a hard time keeping my Ph at 8.2 but all other test were fine. My fish were active the corals for the most part did very well. I used RO/ID water and Instant Ocean Reef Crystals. I have spent several hours reading other articles by you and enjoy them. There is so much information on the forums and chats that you really do not know what or who to believe. I depending a lot on my local fish store where I purchased my marine fish and corals and then reading your articles.

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