Out on the wild reefs corals are obviously left to their own devices. A constant battle is fought for dominance and space with individual struggles sometimes lasting for years. Some corals are much more aggressive than others but all seem to find their place.
In the reef aquarium the potential for conflict remains. If the aquarist has done his/her job with research and advice then this potential is reduced. Corals that are unrelated are not permitted to touch and all corals are given expansion space. They are also positioned according to their need for light and seawater flow.
All things being equal the reef aquarium will be beautiful but despite the aquarist’s care troubles could still occur because corals grow, some more quickly than others. This could cause interference with seawater flow or light and action has to be taken to correct this, this usually being a reduction in coral size by careful trimming. The upside of this is that the coral that has been cut will recover and there is another coral, the cut portion, which is now a new coral ready for growth. If there isn’t enough space in the reef aquarium, then another aquarist or a dealer is the answer.
It can be that the problem isn’t to do with overgrowth at all, but coral aggression because of a demand for territory. This could be seen by the aquarist as whitened ends to one coral while a neighbour is seen to be touching. As already stated some corals are more aggressive than others and the weaker usually has the discoloured ends. All coral struggles are not seen like this as for example if two much less aggressive corals are fighting then any discolouration could be completely missing.
The heading photo shows a coral that had grown a bit too large, it’s the leather coral (Sarcophyton sp) at centre a little to the right. The coral had grown out of proportion and was overshadowing others. The answer in a case like this is simple, some sharp scissors and the head was cut off. Enough ‘stalk’ was left attached and in a very short time new polyps were appearing. Just below this coral can be seen very young specimens of the same kind.
The photo above shows mainly green star polyps (Pachyclavularia sp) which spread on a purple mat. They are not considered aggressive and had given way to button polyps (Zoanthid sp), again not considered very aggressive, which had caused the star polyps to recede in a half circle. The button polyps were completely removed from the rock – one remaining can be seen near the left hand side centre of the photo. As a result the star polyps are expanding back onto the cleared rock space.
Sometimes coral expansion can just be too much for the space available or the desire of the aquarist as it ‘misadjusts the picture’. In this case it needs the coral in question reducing in area. The final photo shows a generally bare rock which was inhabited by several mushroom corals (Rhodactis sp). These were removed one by one leaving a smaller colony (not shown) intact. There is one mushroom to be seen which is at the bottom right corner of the photo. These corals were hard to remove because of their ability to retract very quickly, their slimy surface and their incredible regeneration ability – leave a bit in place and hey, another mushroom. On this rock has been ‘planted’ a very small colony of star polyps which it is hoped will cover the rock in time.
So the reef aquarist has much to look out for, not only the quality of seawater and lighting but the actions of the corals themselves. Coral territorial expansion could take place fairly quickly over a period of months or it could be years, so the two words so often used are here again – observation and patience.