What you need to know about corals
Corals add a beautiful dimension to a reef tank that freshwater fish set-ups cannot even hope to rival.
We explain why these fabulous creatures are truly unique.
With living, growing corals you can decorate your tank and increase its diversity at the same time.
These fabulous creatures come in all shapes, sizes, and varieties simply enhancing their appeal.
They comprise:
Soft corals
These are so named because although they contain calcium in their tissues they do not use a hard skeleton for support, or leave one behind when they die.
They can vary from tiny polyps on small, ground-hugging mats to large mushroom-like or tree-like shapes growing several feet across. Softs are the hardiest corals and are often recommended for beginners. They only need medium-strength lighting and water flow and the mat-forming species generally spread quickly and can be propagated with scissors and placed elsewhere.
Generally, soft corals, especially leather corals, are beige, encouraging experienced reef keepers to move to more colourful hard corals. However, some more sought-after mushrooms and star polyps can be very colourful and will flourish under the correct lighting.
Hard corals
So-called because they all have a hard calcium carbonate skeleton, when one dies the soft tissue and polyps on the outside recede leaving a white, calcareous skeleton which other corals populate and Staghorn hard coral (Acropora sp.). begin to grow on top.
This piling up forms the foundations of a coral reef- and hard corals are also known as reef-building corals.
Hard corals are usually more difficult to keep than soft and more expensive, although much sought after. However, improvements in husbandry and equipment make the culture of hard corals more achievable — even by novices.
Hard corals are comprised of two main groups, LPS and SPS, also known as stony corals.
These are the differences:
LPS corals
These initials stand for Large Polyp Stony or Large Polyp Scleractinian. Generally speaking, they are large,
jelly-like corals that fill with water and surround a smaller, dome-like coral skeleton.
They are popular because of their form and vibrant colours, many of which fluoresce under blue light.
In their natural habitat, LPS corals live in shallow, turbid lagoon environments or deepwater environments. They need medium-powered lighting in aquaria and must be fed on larger items of zooplankton.
When feeding your fish on frozen foods like Artemia you'll note that LPS corals often seek to take these too, extending their large feeding polyps and capturing any floating foods that pass.
LPS corals should be regarded as quite aggressive towards other corals, so shouldn't be placed near each other or they will sting and try to kill each other by extending sweeper tentacles.
LPS will also sting both soft and SPS corals, so give them plenty of space. Because of their large water-filled bodies, LPS corals don't appreciate strong water movement, so place them away from pump outlets. They won't appreciate very intense lighting either, so it's therefore generally best to place them lower in the aquascape.
SPS corals
SPS stands for Small Polyp Stony or Small Polyp Scleractinian. Many species are known and identified as Staghorn or branching corals, as they create large masses of brittle, branch-like arms. On the whole SPS corals will seek out and live under bright sunlight and strong water movement, so these particular conditions must be replicated in your planned aquarium environment. Their sting is not particularly potent, so these corals can be grown close to each other. Once you've got the hang of growing them you can propagate them easily by taking cuttings from their hard skeletons and securing the cutting on some rock with a blob of reef-safe putty. Of all the corals, however, SPS are some of the most demanding and least hardy, so generally are only for the experienced reefkeeper.
Suitable products
Often found in areas of murky and turbid water, open-brain corals are one of the hardest choices for newcomers to LPS corals.
LPS corals such as this often benefit from occasional supplemental feeding with meaty foods such as Mysis or Artemia.
FAQs - We answer some of your most frequently asked questions about corals.
Is another coral touching any and stinging them? Is one of your fish nipping them?