Coral reefs arguably are the most diverse habitats on Earth. All major tax are included in these ecosystems. But, as one might expect, corals are especially abundant and species-rich. Of course there are plenty of stony, photosynthetic, reef-building corals there. But soft, nonphotosynthetic (NPS) corals are richly represented there as well. Many of these NPS …
Corals
Corals are a group of exclusively marine, polyped animals in the phylum Cnidaria. As one can see from their basic body form, they are distant relatives of jellyfish. They can take the form of either individual polyps or colonies of perhaps hundreds or thousands of individual polyps.
They are divided into two basic groups, namely the hard corals and soft corals. Some may be surprised to find that these two groups aren’t very closely related; in truth, stony corals are more related to “normal” anemones whereas soft corals are more related to tube anemones (i.e. cerianthids).
They occur in many ocean habitats from deep waters, temperate waters or shallow tropical waters. However, it is the latter type that most aquarists are familiar with. It is in tropical reefs that stony corals predominate. These produce a hard, stone-like skeleton made of crystalline calcium carbonate called aragonite. They are the so-called reef-building types and are primarily responsible for the formation of the reef itself (the crusts, shells or tubes of certain algae, mollusks, worms, etc., which are also made of calcium carbonate, make some smaller contribution). Chunks of these deposits are known (especially by aquarists) as live rock.
Soft corals, including the gorgonians and sea fans, produce no such calcium hard skeleton. They may, however, produce a leathery (e.g. leather corals) or horny (e.g. gorgonians/sea fans) “skeleton.”
Most reef-building corals and many tropical soft species have a mutually beneficial relationship with special unicellular algae (called zooxanthellae). These algae live within the host’s gastrodermis. Up to 90% of the carbon fixed by the algae via photosynthesis is taken up by the coral. Similarly, certain bacteria known as diazotrophs supply a source of fixed nitrogen to the animal and its algal symbiont, and in return feeds on their organic waste products. Increasingly, the coral animal and its many, diverse microscopic partners are viewed as a single super-organism referred to as the coral “holobiont.”
In addition to these symbiotic relationships, many prey on zooplankton or even tiny fish (depending upon species and size). The coral uses its tentacles, armed with stinging cells (i.e. nematocysts) to stun, hold and kill its prey as it moves the item into its mouth. Following digestion, the waste is excreted from the same opening.
Success with these fascinating and beautiful creatures in captivity requires regular feedings of each species’ preferred food source(s) as well as intense illumination to promote photosynthesis of the zooxanthellae.
In this section you will learn which corals prefer which types of light and foods, as well as how to create the environment (e.g. water conditions) that they need to survive and grow.
Keeping Turbinaria Corals
Do the terms SPS or LPS really mean all that much? Because we aquarists do tend to infer quite a bit about the care of different coral genera based upon these designations. So what does that mean for genera like Turbinaria? Because some authors describe them as one type, and other authors describe them as …
Keeping Nephthea Corals
No matter how obsessed reefkeepers get with their “sticks,” the visual appeal of soft corals is undeniable. Few aquarists could ever resist having at least one or two softies waving in the current, and we see this in most of the systems we encounter in forums, social media, in LFS show tanks, etc. With its …
Keeping the Bubble Coral
Nothing turns an aquascape into an artistic masterpiece like a huge coral specimen. Whether a massive acro colony, leather coral or whatever, they serve as centerpieces that create a focal point and impart a pleasing visual balance. And, well, if they’re really impressive, they also function as a conversational piece. Arguably, few corals “work” as …
Keeping Plate Corals
A freshly set up and cycled reef aquarium is something like a fresh canvas–a seemingly vast, open aquascape. Following our impulse to start covering the hardscape, we tend to start stocking corals by mounting a fistful of frags over the top of the rocks. A beginner reef aquarist in particular might first test the system …
Keeping Pavona Corals
Many aspiring reef aquarists are a bit intimidated by SPS (small-polyp stony) corals. This is not without good reason; generally being more particular about water flow, lighting and water chemistry, they are well within the realm of the advanced aquarist. But we say “generally” in this case because there are some exceptions to this rule …
Keeping the Birdsnest Coral
As a group, SPS corals can be endlessly frustrating, even for veteran reef aquarium hobbyists. For beginner reefers in particular, it can be satisfying to witness some success with this group not just through mere survival, but also through clearly observable growth. For those who are eager to see their little “sticks” get bigger, or …
Keeping Sinularia Coral
Thanks to huge improvements in technology as well as better livestock supply chains (including an ever-increasing availability of captive-raised specimens), more reefkeepers are enjoying success than ever before. That being said, no veteran hobbyist will ever be able to honestly say that maintaining a reef tank is completely without challenges–nor disappointment. Even the most experienced …
Reconsidering Soft Corals
The domination of the reef aquarium hobby by stony, and especially SPS, corals is pretty obvious. An overall increase of our understanding of growth factors such as lighting technology and alkalinity management have boosted success with such “reef building” coral species across the trade. That notwithstanding, scores upon scores of attractive soft coral species are …
Branching Green Star Polyps: Trash or Treasure?
The aquarium hobby in general, and certainly the reef aquarium hobby in particular, has changed a whole lot over the years and decades. As aquarists master the husbandry of new species, some “classic” species might lose their luster. For example, where Xenia was once a beloved coral for its ease of care and pulsing behavior, …
Keeping Toadstool Leather Corals
These days, soft corals don’t get quite the attention they once did. One reason for this simply is the abundance of wildly colorful stony corals that have fairly recently become available. Another reason is the concern that soft corals can release allelopathic substances into the water that may harm other (especially stony) corals. Even so, …
Upgrading to the ULTIMATE Ecopack
Pods. Phyto. At AlgaeBarn, these are the bread and butter of the reef aquarium diet. And for sure, these two items form the base of most freshwater and marine food chains. Just consider OceanMagik, which is a blend of four distinctly different species of phytoplankton. Or EcoPods, which is a mixed-species (four, to be exact) …
Do Corals Really Eat Plankton?
It’s hard to say for sure which came first for reef aquarists–the emergence of high-quality coral foods, or the realization that corals actually, really, truly do eat them. Though aquarists are generally a skeptical bunch, the initial apprehension to feeding corals is pretty understandable; in all fairness, many such foods sold in the recent past …
Natural Water Quality Management for Non-Photosynthetic Reef Aquaria
There was once a time when zooxanthellate corals (especially SPS corals) were considered impossible to keep in captivity. Then advancements in aquarium lighting technology changed all that. It’s hard to imagine that there so recently was a day when marine aquarists abandoned the possibility of ever keeping Acropora–one of the most abundant genera of stony …
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What Do I Need for a Saltwater Fish Tank?
Whether scouting for your first aquarium, or “graduating” from a freshwater aquarium, there is something about a saltwater aquarium that is mesmerizing. For many lifelong aquarists, that feeling of captivating awe never goes away. Thankfully, the intimidating task of learning how to actually build and maintain a saltwater aquarium system does go away. In fact, …
Keeping a Coldwater Marine Aquarium
Marine aquarists have always had access to temperate species. In fact, in the days before improved packaging/shipping procedures allowed for the massive import of tropical species that we enjoy today, most saltwater aquarium livestock originated from temperate waters. Catalina gobies, waratah anemones, garibaldi damsels… At least half of the seahorses… The coolest boxfishes… Anyone who …
Knowing the Zoanthid
The zoanthid is one of the most stunning yet simplistic coral-like animals in this hobby. It can come in any color combination that you can imagine–along with any price point. This is why this particular anthozoan deserves an article of its own. There are over 100 species of zoanthids alone and the identification process can …
3 Most Expensive Corals
For people that are new to this hobby, it is sometimes hard to grasp just how expensive certain corals can be. In this article I will be discussing the most expensive corals (well, corallimorpharians and zoanthids, to be technical) and the reasoning behind the price. Most of the time, the price is due to high …
How to Get Rid of Aiptasia
When you’re first starting out your aquarium, you usually will spend all day checking on everything in your tank ensuring everything is still intact. Then, one day you look and you see this translucent looking pink flower… I receive one of two reactions from customers when they first come across Aiptasia anemones. One is panic. …
When to Choose Poseidon’s Feast
Back in “the day,” to acquire a seed culture of copepods, aquarists would typically have to resort to scooping a couple cups of gravel from the bottom of a fellow aquarist’s tank. In these cases, you could only hope to have nabbed a few viable pods–and not any pests (like juvenile aiptasia anemones)! If you …