Order Alcyonacea, Family Alcyoniidae, Genera Sinularia, Sarcophyton, Lobophytum, Alcyonium, Cladiella, etc.
Common names: leather coral, colt coral, toadstool/mushroom coral, tree coral, etc.
Natural origin: Indo-Pacific
Sensitivity (Level 1): These corals are usually exceptionally tolerant and forgiving. They're also easy to fragment and propagate. Beware of dyed corals (pink leather corals have almost certainly been dyed).
Feeding: These corals have extensive feeder tentacles. They feed on very small particle food. Some are pickier eaters than others, so variety is helpful.
Lighting (Level 3 to 8): Though adaptable, most prefer more intense lighting conditions. If kept under less light, be sure to feed well.
Water flow: To avoid sediment damage, moderate to strong water flow is preferred.
Placement: It's important to note that some species are highly toxic to stony corals (especially larger polyp stony corals in the genera Lobophyllia, Symphyllia and Trachyphyllia). Since specific species identification of leather corals can be quite difficult (sometimes even to identify a genus), these corals should be added with reservation to any tank with stony corals. Also consider that many leather corals are relatively fast growing and can get quite large. However, this isn't usually so much of a concern since they can be literally cut down when they get too big.
General: Leathers are great corals for beginner aquarists or anyone looking to keep more low maintenance corals. Note that when stressed or introduced into a new tank, they may close up and not open up again for several days or even weeks. This might also happen right before the coral sheds. Stronger water flow will decrease the "shut down" time before shedding. This periodic shedding of the outer layer of cells is a normal occurrence and is thought to help keep algae and/or other corals from growing over them.
It's important to keep the toxicity issue in mind. Someone hoping to keep larger polyped stony corals at a later time should think carefully about adding leathers to their tanks, especially those in the genus Sacrophyton which are known to be particularly toxic.