Invertebrates Coelenterates

The Coelenterates constitute a complex group. They include the Anthozoa, which are divided into hexacorals, where the number of tentacles is a multiple of 6, and octocorals, where the number of tentacles is a multiple of 8.
The hexacorals are divided into:
- Actiniaria (true anemones);
- Ceriantharia;
- Zoantharia (colonial anemones);
- Corallimorpharia (discus anemones);
- Scleractinia (madreporites or true corals).

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When well acclimatized, the Coelenterates soon deploy their tentacles, which is a sign of good health.

These invertebrates are characterized by tentacles attached to a foot, and the whole organism is called a polyp. Anemones and Ceriantharia are isolated polyps, while the other Anthozoa are colonial polyps, connected to each other at their base, which ends up by spreading out over large areas like certain plants.

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What If You Touch a Coelenterate?

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The bodies of Coelenterates, particularly the tentacles, are covered with urticant (stinging) cells, equipped with a strand that is sensitive to contact with other organisms. When a Coelenterate is touched, thousands or even millions of cells open and eject a filament with a microscopic dart at the tip which injects venom; in this way, a prey is quickly paralyzed before being eaten. Care should be taken when handling, therefore.

Some species have a greater stinging capability than others. Serious reactions, such as cramps or breathing difficulties, rarely encountered among aquarists, can be provoked by certain medusas (jelly-fish), due to a phenomenon known as anaphylaxis: the body is sensitized to the venom after an initial contact and becomes more vulnerable.

In the event of an accident, detach the tentacles and, above all, do not rub your eyes. Treat the stung area immediately with diluted ammonia, but it is best to consult a doctor.

Introducing Coelenterates to an Aquarium
Coelenterates must of course present all the necessary signs of good health before being introduced to an aquarium: they should be unfurled, swollen, and full of water. If they are in a bad state, they look wilted and may not be viable.

Anthozoa like clear and well-lit water, as it benefits both them and the Zooxanthellae to which they play host. They must be placed close to the surface of the aquarium. The water quality is, of course, very important, and in addition the calcium levels must be monitored with particularly close attention.

The skeleton of corals is mainly composed of calcium carbonate, which is abundant in the natural habitat - up to 500 mg/liter - and so an aquarium that is to be inhabited by corals must also have the same level. The concentration in an aquarium can sometimes fall below 300 mg/liter, depending on how many organisms there are in the tank, and in these cases calcium must be added.

When Must Calcium be added?
Calcium is added when the concentrated measured is less than 400 mg/liter. There are tests on the market to measure the quantity of this parameter. Remember that the measurement of CH, in sea water, reveals the quantity of carbonates and bicarbonates. When this is less than 7°CH (128 ppm), it can be concluded that a lack of calcium carbonate is more than likely and steps should be taken to remedy this.

Zooxanthellae
These are green micro-algae which live in the skin of Anthozoa and other organisms, such as sponges or giant clams, a type of bivalve mollusk. They exchange substances with the cells of their hosts. The carbon dioxide (CO2) resulting from the metabolism of the cells - i.e. the oxidation of the foodstuffs - is collected by the Zooxanthellae.

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The green coloring of this Anthozoa indicates the presence of a significant number of Zooxanthellae: this animal must therefore be placed under fairly intense lighting.

These, in their turn, absorb nitrogenous and phosphorous substances, carry out photosynthesis, and produce organic substances that enhance both their own growth and that of their host. This type of mutually beneficial association taking place inside an animal is known as endosymbiosis. The Zooxanthellae contribute, to some extent, to the feeding process of Anthozoa, which therefore need only a very scanty external supply of nutrients: some organisms, such as the anemones, need to be fed only around once a week in an aquarium.

Coral Reefs
The accumulation of calcareous coral skeletons gradually forms reefs, of which the most famous is the Great Barrier Reef, stretching north-eastward from south Australia for almost 2,000 km. It is the biggest structure of animal origin in the world! This ecosystem, one of the richest and most diverse in existence, is also fragile and constantly subject to attack. The last few decades have witnessed the destruction of some reefs, the coral being used to build houses, roads, and even airport runways!

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Obviously, aquarists have been accused of taking part in this pillage, which seems grossly exaggerated: the removal of corals from their natural habitat for the aquarium trade does occur, but it is negligible compared to other large-scale extractions. Furthermore, some species are protected by law and never reach hobbyists' tanks.

Public marine aquariums can, on the contrary, make a contribution to the study of invertebrates. The aquarium of the Monaco Oceanographic Museum, for example, is carrying out research in this field, using a 40 m3 tank containing several tons of corals, which are nurtured and bred. Until recently, raising corals on this scale in captivity was impossible, above all because of their very great sensitivity to nitrates (NO3-).

Scientists solved this problem by allowing these nitrates to turn into nitrogen gas (N2), thanks to the anaerobic bacteria which survive at the bottom of the tank, where the oxygen levels are low. The nitrogen produced by the metabolism of these bacteria then passes into the atmosphere. This complicated technique is beyond the reach of most aquarists, however experienced they may be.

How To Supply Calcium to a Coral Aquarium

Method 1
From the start, i.e. when you put the first water in, use commercial salts enriched in calcium. Then, add the same salts over the course of regular partial water changes, at the rate of 10% per week.
Method 2
Use commercial products specially prepared to increase calcium levels.
Method 3
Place a calcareous element, such as calcareous rock, or crushed and washed oyster shells, in the filter, and this will gradually release calcium. However, this method will not give rise to any rapid or significant increase in calcium levels.
Method 4
Prepare a solution of slaked lime, Ca (OH)2 , available in aquarium stores, at a rate of 1.5 g/liter. Pour in 1 ml of this solution per liter of sea water. Proceed gradually, monitoring the pH constantly to ensure it does not rise above 8.5.
Method 5
This is the most complicated, but also the most effective.

Prepare two solutions:
- one of dehydrated calcium chloride (CaCI2 , 2H2O) at a rate of 15 g/liter, which will provide the calcium;
- the other of sodium bicarbonate (NaHCO3 ), at a rate of 17 g/liter, which will provide the carbonates.

Then calculate the difference between a carbonate hardness of 130 ppm (7.2°CH) and the one measured in the aquarium. Multiply the result by the net volume of the tank, and divide the result by 10. This will give the amount of each solution required, in milliliters, to pour into the aquarium.

Example: for a tank with a net volume of 500 liters, with a carbonate hardness of 100 ppm (5.6°CH), the result is:
Amount of each solution (in ml) = 500 x (130-100) + 10 = 1,500 ml.
The following table gives you the required amount of each solution (in ml) for specific cases.

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Feeding Coelenterates
By filtering the water, the Coelenterates trap small suspended particles, particularly the crustacean zooplankton. Collecting, keeping, and distributing plankton is not a task to be taken lightly, and it is best to look for other solutions. However, it must be made clear that commercial foods on the market provide little more than a stopgap.

The leather corals of the Sarcophyton genus will not tolerate being dose to Coelenterates highly prone to stinging.

It is possible to use rotifers or freshly hatched brine shrimp nauplii, normally used as the main food for fish, but not everybody breeds these animals. There is another food which is available to all hobbyists, as it is inexpensive, easy to make, and can be frozen: it is usually called mussel choppy. Mussels are not only cheap but also rich in proteins, carbohydrates, mineral salts, and vitamins. Other possibilities are cockles, the flesh of lean fish, or cans of shelled shrimps, which are produced in large quantities in Asia, cost little, and are readily available.

The other problem is establishing a feeding schedule. It must be remembered that the majority of organisms being fed play host to Zooxanthellae, which often satisfy a significant proportion of their dietary needs, and so a weekly feed is more than sufficient. Do not forget that the best time for this is the night before a water change, to reduce the risk of pollution. The larger anemones feed on adult brine shrimps, small pieces of mussel, fish, or shrimps or a mixture of these.

Food For Coelenterates also Sponges: A Recipe
Ingredients:
- mussels or cockles;
- white fish, i.e. lean and free of lipids;
- shelled shrimps in cans (optional).

Cook the mollusks and fish. Put the shrimps in boiling water for 1-2 minutes.
Remove the mollusks' shells.
Mix all the ingredients thoroughly. You can add a vitamin solution, flakes or granules of fish food, boiled spinach, or the special foods for invertebrates available commercially. If the paste is too thick after mixing, thin it with saltwater.
Pass the mixture through a sieve. What is left behind in the sieve can be distributed to anemones or small fish; this puree can also be frozen. Allow the puree to stand for several hours in the refrigerator, then discard any excess water.
The resulting paste can be used straightaway for feeding, or can be frozen.

In their natural habitat, Coelenterates feed on animal plankton, but these are difficult to supply in an aquarium.

It is best to put the food into the aquarium at night, 1 or 2 hours before switching off the lights.
Switch off the filters, pumps, and aeration for a moment.
Thaw the food, if necessary, and distribute the equivalent of one tablespoon of the prepared liquid for every 200 liters of water. Deposit the food above the invertebrates with a narrow, rigid tube. The filtration and aeration systems can be switched back on a few minutes afterwards.

Compatibility Between Coelenterates
Urticant (stinging) Coelenterates must be kept apart from the more delicate species: a safety margin of 10-15 cm is often recommended. The madreporites and anemones are among the most urticant, and they must not be put alongside a leather coral from the Sarcophyton genus, for example. Other alternatives for a Coelenterates tank are algae – whether encrusting or not - supported by live rocks, or even caulerpae. Their development must be controlled so that they do not end up smothering the Anthozoa.

The Coelenterates can cohabit with algae - encrusting or otherwise - and even with small fish.

The introduction of certain fish is possible, even desirable, but there are cases of classic incompatibilities. Specially designed artificial decor can be colonized quickly, depending on the organisms' rate of growth and reproduction. This can sometimes make it difficult for even a practiced eye to spot the difference between artificial and natural decor in an aquarium which has been in operation for several months.

Coelenterates are the favorites among aquarists that specialize in invertebrates, although their availability - and their price - can vary enormously. Furthermore, there is sometimes confusion over their names: some species may not even have one as they have yet to be systematically studied and described!

Saltwater Introduction

Cover all we need to know about saltwater, so we can keep marine fish.

Aquarium Supply

Lot of things we should prepare to start saltwater aquarium!

Aquarium Setup

Steps to be taken before the aquarium ready to receive
fish and operate.

Marine Fish

Detail about saltwater fish species. For beginner also expert.

Invertebrates

They difficult to keep, although there are some suitable for hobbyist.

Plants

There’s only a few of them, but the results can often be highly attractive.