True corals or madreporites live in a calcareous skeleton, into they which they can withdraw. This skeleton means that they make the most significant contribution to the building of coral reefs in tropical seas. These are the most difficult invertebrates to keep in a marine tank, as they require well-aerated water of the highest quality, with no suspended particles - and therefore crystal clear - and an extremely low nitrate content. As they are very sensitive to nitrates, it is essential to partially change the water on a regular basis, in small volumes. The tentacles, often drawn in by day, unfurl at night to capture food. This does not mean that corals like darkness; on the contrary, they must be provided with a great deal of light, on account of the presence of Zooxanthellae. They are carnivorous, feeding on animal plankton in their natural habitat and a choppy based on mussels or fish in captivity, once a week. A supply of calcium carbonate is desirable for the growth of the skeleton. Take care when placing them in an aquarium, as they should not come into contact with other Anthozoa once their tentacles have unfurled.
They are rarely imported alive but their skeletons are often used as decor in domestic aquariums. In the wild, their growth is rapid (a few centimeters per year) and they can exceed 1 m in height. Height: 20-50 cm. Fungia (Fungids) These solitary (and therefore non-colonial) corals generally live on the sediment and do not take part in the construction of reefs. The distinctive skeleton can be used as a decorative feature. Diameter: 20 cm. Goniopora (Poritidae)
The species from this genus are imported on a fairly regular basis, and are some of the easiest to keep in an aquarium. They prefer moderately aerated water. Size: 20-30 cm Favia, Platygira (Favidae) These are easy to keep in captivity and accept small, live prey. The colored tentacles are drawn in by day. Size: 20 cm
One temperate species in this genus also tolerates tropical temperatures: Leptosammia pruvoti.
Its yellow-orange color and small size make it good for decoration. It is preferable - in fact, essential - to put it into the aquarium already attached to a support. Size: 5 cm. Plerogyra (Caryophylliidae)
The species in this genus, known as bubble corals, are quite easy to keep in an aquarium. The daytime "bubbles" withdraw at night to give way to stinging tentacles 1-5 cm long. In the wild, the bubbles provide the coral with a certain degree of protection, as the tentacles are not attacked by fish (butterfly fish, for example). The color of the bubbles varies depending on the presence of Zooxanthellae, and these mean that this coral requires strong lighting. It is best to feed it at night - when the tentacles are unfurled - with relatively large, live prey. It is also possible to accustom it to eating a fine choppy based on seafood between the bubbles by day. Avoid allowing the bubble coral to touch other invertebrates, on account of its capacity to sting. Size: 20-30 cm
Half-open Plerogyra sp Some tentacles are visible; the green color is the result of Zooxanthellae.
These live in colonies in both temperate and tropical seas. They are able to build a skeleton, but it is not the same as that of the madreporites. Their tentacles, numbered in multiples of eight, are 1-5 cm long. Their reproduction is either sexual or asexual, through budding. As with the hexacorals, some species can house Zooxanthellae.
Sinularia sp., soft coral from the Indo-Pacific region.
Alcyonarians (or soft corals)
These live attached to the substrate by a horny secretion, and their polyps can be withdrawn. The presence of Zooxanthellae means that they require strong lighting.
When they expel water from their tissues to renew it, they look like leather, hence their name leather corals. They are easy to keep in well-aerated water and they grow quickly. Their color varies according to the concentration of Zooxanthellae present.
Their weekly diet consists of a fine choppy of mussels and other seafood. They must be positioned with care in the aquarium, well away from other stinging species. Two leather corals are most commonly found in the aquarium trade: Sarcophyton glaucum and 5. trocheliophorum. Size: 20-30 cm.
Sarcophyton sp., closed (left) and with the polyps extended (right). •
The species in this group, which comprises several families, present a ramified, fan-like form and can grow to a height of 2 m. Their skeletons can be used for decorative purposes. These animals prefer a fairly dark environment, where they live attached to a support. They sometimes have a tendency to be colonized by other organisms, such as sponges or filamentous algae. Their food must be very fine and distributed daily. Size: 15 cm.
A FALSE CORAL, A TRUE GORGONIAN
The red coral (Corallium rubrum) found in the Mediterranean, up to a depth of 200 m, is in fact a Gorgonian. These days there are no colonies over a few dozen centimeters, and their disappearance can be attributed to fishina off the coasts of France, Sardinia, and Tunisia that is so intensive it is best described as pillage! Such demand is exp lained by the fact that the bright red skeleton of this species is used in jewelry (particularly so in Italy)
Worms belonging to the genus Sabellastarte are sometimes imported. The branchial plume (in a double crown) can reach 15 cm in diameter. It is best to keep them away from stinging Anthozoa. Their diet is the same as that of the Coelenterates.
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