The term soft corals is a relatively unscientific way 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 mushrooms or zoanthids).
Unlike LPS and SPS corals, which have a substantial external skeleton made of calcium carbonate, the soft corals have very large, soft, fleshy polyps with tiny pieces of calcium carbonate skeleton included into their tissue. These tiny pieces of skeleton, called sclerites, look like tiny crescent moons or even fingernail clippings. If you look closely, you can sometimes see these sclerites embedded in the tissue of certain corals.
Unlike zoanthids and mushroom corals, soft corals 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 soft corals.
The true soft corals belong to the octocorillian family, 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. Zoanthids, by comparison are hexacorals and have a different body structure than the true soft corals. The most common soft corals in the hobby are part of the Alcyoniidae family…which is the same thing as saying they are leather corals.
- Cladiella–colt corals, including kenya tree coral
- Pachyclavularia–green star polyps
- Sinularia–cabbage leather coral, finger leather
- Lobophytum–devil’s hand
- Pulsing xenia
It is a bit tricky (or imprecise) to try and provide care instructions for a grouping of corals as large and diverse as soft corals. But what I will do here is try to focus on the most commonly available varieties.
Soft corals 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, capnella, colt corals and other similar corals. Standard reef aquarium water parameters will grow these corals well.
To 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 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.
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. 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.
Fragging soft corals is fairly straightforward. 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. Attaching them can be a bit more challenging because they typically are not able to be glued into place.
Soft coral frags are the escape artists of the aquarium world, so you have to use a plastic container and mesh, rubber band or toothpick method to attach them. You can find step-by-step instructions for all of these in How to Frag Corals.