To classify a wide range of coral species that are both related and unrelated into a single category characterised mostly by what they are, the term “soft coral” is employed in a broad meaning and in a fairly unscientific way.
And the parts they don’t have
Despite what their names would imply, these are not synthetic corals as the Mushrooms are. Reading about any of this is important and worthwhile since many of these fantastic species (yes, they are animals) are some of the most common, easily available, and low-maintenance aquarium corals you will come across in this hobby. But only taxonomists care about getting the categorization and taxonomy correct. Since we care about our reef tanks’ inhabitants, let’s dive right in and learn more about what it takes to keep the soft corals happy and healthy in a saltwater aquarium.
Compared to its softer sibling, soft coral, what distinguishes hard coral?
It is the presence of a substantial calcium carbonate exoskeleton that distinguishes hard corals like the LPS as well as SPS.
Soft corals have bigger polyps that are fleshier and softer than those of zoanthids corals, and their tissues include minute fragments of calcium carbonate skeleton. Sclerites are small pieces of the skeleton that look like little crescent moon or even the fingernail trimmings (eww!). Sclerites may be found in every organ of the human body.
Sclerites like this may be seen embedded in the tissue of some corals, but only with a magnifying microscope. Check that lovely carnation soft coral down there!
Can you make out the white striations that traverse the carnation soft coral’s skin?
This is the soft coral’s typical, less stony skeleton, and it’s called sclerites in spite of the fact that it is more challenging to notice them when the tissue is not transparent, they may be found in any kind of tissue.
Broken bones are really made of calcium carbonate
In both LPS and SPS corals, this stony skeleton material is present. Calcium carbonate shards create the lines on coral that look like striations or even worms. This genus of corals lacks the more formidable rocky structure of a Gonipora, which contains huge polyps that seem soft but originate in a stony skeleton, like the Trumpet coral in the centre picture below. One of the key features of this class of corals is the lack of that structure.