When an aquarium is ready for coral stocking, or is up and running and additional coral stocking is being contemplated, a trip is usually taken to the local retailer to decide on what to purchase. On arrival, more often than not there is a large range of corals on display of both the hard and soft varieties, though the latter may be in higher numbers.
The choice can be bewildering. What to choose? It is said over and over again that research into potential stock before purchase is very important. Inappropriate corals are still purchased though. Many, maybe most aquarists do it. I did.
The corals look so splendid, but there are some that stand out. There are others that really stand out, and it is with these that the aquarist is overcome. So they are bought.
The first is a soft coral. Soft corals are supposed to be ‘easier,’ and so they are generally. There are always exceptions, and this is one of them.
The coral is commonly known under several names- carnation coral, tree coral, strawberry coral and cauliflower coral being some. The proper name is Dendronephthya. There are perhaps 250 different types under this banner. They are really colourful, coming in purple, red, yellow, white, green, pink and orange. Without doubt they are beautiful – attractive is to do them an injustice. I feel quite certain that they will sell quite easily simply because of their visual appeal.
So what is the problem? Most corals help the aquarist by having symbiotic algae (zooxanthellae), which, with adequate light, greatly assists in the maintenance of the coral by providing food and ridding the corals of waste. Dendronephthya do not have this algae. They obtain food by capturing it. To survive a high level of phytoplankton and possibly zooplankton are required. This means, in a closed system, a great danger of pollution. Also the corals require fairly strong currents to bring the food to them which may not suite some other corals. On introduction to the aquarium, some do not even re-expand. Even if they do they are likely to perish quite quickly. As said, if sufficient food is provided it is likely that the tank will be polluted and then more than this coral will be negatively affected. The only good thing about the coral (apart from its beauty) is that in nature they are found in areas of very low light and also, but less, in areas of sunlight. Therefore it may be that they can tolerate many positions in the aquarium. However, be that true or not, they are not going to survive anyway.
The second coral that requires a mention is for the same reasons – difficulty of maintenance. This coral is possibly even more attractive than the one already mentioned. This is the one that I purchased (once) years ago.
In this case the coral is commonly known as the flowerpot coral or daisy coral. The proper name is Goniopora, and they are hard corals. They can be brown, green, cream, pink or yellow. Their beauty comes not only from the colour but also from the long stems of the polyps, hence the common names. These do look like flowers in a vase, and they sway in the currents in a really attractive way. They can easily be the centrepiece of any aquarium.
They are often sold as a round ball like rock, with the coral covering most of the upper and uncovered surface of the rock. The ’skin’ of the coral seems to be stretched tight over the surface of the rock and this is the first danger. The aquarist can unwittingly damage the coral when putting it into the aquarium if the support rocks are sharp, or there is insufficient support and the coral falls. Great care needs to be taken when handling these corals and their placement pre-checked.
They prefer low to moderate currents because of the long polyp stems, and also bright light. So in an aquarium lit by fluorescent tubes the coral needs to be placed high on the reef.
The second problem is with feeding. It is reported that Goniopora cannot survive on their zooxanthellae, therefore supplementary feeding with phytoplankton is said to be required. So the same problem can occur as with the first coral if due care isn’t exercised – pollution.
Even if all apparent requirements are being met it is likely that the coral will fail. It may last a month or longer, but the high probability is it will die. This happens slowly, the first indication being that the polyps, or some of them, are not expanding as much as they used to. Eventually, the polyps hardly expand at all, and more and more fail to open.
Some aquarists keep Goniopora for a ’long’ period (’long’ in terms of the expected captive lifespan of this coral) which could be 6 months to a year. In my case it was about 8 months. My coral didn’t die because of failure of the polyps, though they were quite short and, if I recall correctly, some didn’t expand at all and some polyps didn’t open, it died after a fall from the rockwork. There wasn’t any obvious damage, but the coral became covered in a jelly-like substance and that was it.
Very advanced aquarists who may wish to experiment with the captive care of the two mentioned corals could be of great benefit to all of us. Experiments with feeding, water currents and light could be undertaken.
For the rest of us, the corals should not be purchased, and the magnet of their undeniable beauty resisted. As far as I am aware they are not threatened in the wild, but surely it is wrong to sell or buy corals that are very nearly 100% certain to die. Better to leave them to survive with nature until the secrets of keeping them in good health in captivity are known.