Corals And Bacterial Disease

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Reef enthusiast
Corals and Bacterial Disease

By Albert J. Thiel

At times the corals we have in our aquariums develop a disease characterized by brown slime or brown stringy matter floating over them, while being attached to them, although it is not easy to see where. Indeed this slimy material seems to "float" above the coral in a certain ara. Often too, this disease, and its result, is hidden (not visible) between the coral's tentacles for a certain time, and not all that discernible (if at all) until polyp loss, and other damage to the polyp or polyps has, or may have, occurred.
This is unfortunate of course, as indeed degradation of the polyp(s) may have occurred and damage may have developed already as well. This cannot be avoided unless the hobbyist carefully inspects his or her corals daily, to make sure the coral is clean and nothing is growing or deteriorating (even hidden) between the tentacles. Bacterial disease starts and is often not detected early enough is what I am saying, to arrest damage before it happens. The fact is that even with the best of all intentions we cannot always avoid this.

Granted, this type of inspection is not a real practical solution but it can certainly avoid damage before it gets extensive and the polyp does not regenerate because the disease is too far advanced.

What we are talking about here, as you have surmized, is bacterial disease. The brown filaments or masses floating over and above a coral are sure signs of it. They tend to develop slowly and then suddenly, one morning, there is a whole mass of them. Often the mass appears to be brownish and somewhat transparent. It can easily be mistaken for algae growing on the coral. It is not.

One way we can implement to minimize damage to corals is to ensure that all of them receive good laminar water current flow over their bodies (polyps). This often prevents bacterial infections and the ensuing bacterial disease and the associated degradation of the coral from even starting.

Let us look though, to begin with, at what causes these infections and what happens when the disease sets in. Additionally, let us look at what we need to do when bacterial disease occurs and what we can do to prevent it from happening (at least for the greater part, as avoiding it completely is not always possible, however much we would like it to be so). Let us look too at what we can do to arrest it.

Potential Causes

Corals are in an environment of real low water quality parameters:

High levels of total nitrate are often the cause of bacterial disease.
Total nitrate is calculated by taking the nitrogen-nitrate reading your test gave you, and multiplying that number by 4.4. Note that most tests on the market give results in N-NO3 and not in "total" nitrate. Normally the instructions that come with the test will say so. Some do not. If you are unsure about what your test really measures, you can always resort to calling the manufacturer.

When your N-NO3 level is high, e.g. between 60 and 80 ppm, your real nitrate level (total nitrate) is really between 260 and 350 ppm.
This is extremely high, and sure to endanger your corals and your fish as well. Fish suffer from high nitrate levels in the tank too.

High phosphate levels may contribute to this too, as they will result in wild, and sometimes totally unexpected, growths of undesirable micro-algae. These can, and often do, grow on the corals skeleton(s) and may start affecting the polyp too if the growth continues. Remember that some algae give off toxins (releasing them on the coral polyp if that is where the algae growth is occuring).

High silicate and silicic acid levels (ppm) give rise to the appearance of diatoms (hobbyists refer to them as brown algae). This can affect the corals too and often does. The real danger lurks when encrusting diatoms start to grow on the skeleton of the coral, start moving upwards along the skeleton, reach the polyp, and start pushing the polyp out of the way. When this happens, the polyp detaches from the exoskeleton and loose fringes of polyp are/may become visible. Sometimes these polyps die off and holes or bare patches on the skeleton (missing tentacles of the polyp) are clear evidence that this is what is going on.

Other Potential Causes

Besides the water quality deterioration or bad condition of it, there are other other causes that can lead to the onset of bacterial infections. The main ones are related to damage that occurred to a coral, the damaged area gets infected and bacterial disease follows.

Here are some of the reasons:

-An urchin, while crawling through the tank, inflicts a scar or puncture to a coral
-Sweeper tentacles from other nearby corals can sting a coral and leave a puncture of damaged area behind.
-A piece of rock falls on a coral and causes a puncture or damage.
-Bristle worms gnaw at a coral and cause damage.
-A mantis shrimp with its razor sharp front mandibules causes damage when it touches a coral or brushes it while roaming around the aquarium
-A fish causes damage in the process of touching a coral, possibly through sharp gill end, or in the case of Tangs, the brushing of their back razor sharp protective modified partial fin against the coral.
-Any fish that eats polyps damages a coral (e.g. Angel and Butterfly fish - I include Pygmy Angels in this category by the way as some will harass corals and may damage them in the process).
-Hermit Crabs can cause damage.
-Small algae eating crabs can do the same, inadvertently but with the same end result.
-Stone crabs moving around and touching corals or rubbing their claws against them, even if not on purpose.
-Some shrimp may do the same, even inadvertenly.
-Some nudibranchs (most are carnivorous) feed on corals or leave toxic excretions behind.
-Detritus that accumulates on corals, rots and is not removed by current will eventually damage the polyp of a coral to the point where the damaged part can easily become infected.
-Some sea slugs
-Wrasse that are not reef compatible present in the aquarium. In this respect it is very important for hobbyists to ensure that whatever they add to their tank, is compatible with what is already in the aquarium. This applies to any type of animal you add not just corals and fishes.
-Some snails that get onto the coral leave toxins behind as they crawl along. These toxins may harm the polyp. The secretions left on the polyp may, in fact, harm the coral and cause damage.
-Small worms that attach to corals (usually white and round type worms). They are hard to eradicate and multiply rapidly. Another document will be added to the Main Library to deal with the eradication of these worms. In brief though, irritants have to be used so they detach and can be siphoned out. Some fish eat them. Six-Line wrasse are a good fish to try out.
-Algae that touch corals can, while excreting toxins and general excretions, damage a coral and so on.

This is a pretty good overview and you should have gotten the picture from this list how easily, indeed, damage to a coral can occur.

Corals And Bacterial Infections (cont)

Remember that "any" damage can develop into bacterial disease.

As you can see, damage to corals can be inflicted by may animals, even several we do not suspect of causing it. Lesions, punctures, sores, and so on, can all result in or to progress to bacterial infections! A lot of the reasons for this are not known, although water quality is certainly one of them (in the true sense it is the lack of good water quality that causes it as this condition is conducive to many bacteria and microbes being present in the water. Good water current directed at a coral can keep such from getting a hold and developing into a full-fledged infection, but no guarantees can be offered in this respect.

At times, regardless of what you do and how good you manage the life forms in your tank for compatibility, damage to corals may occur and bacterial infections may break out.

What to do when a bacterial infection is present?
Below are some suggested techniques you can use. You can use only one of them, or several, or any combination of them:

As indicated previously, make sure that the laminar water currents in your aquarium that go by and over corals are strong. There are some exceptions of course (check details in articles that deal with specific corals -- _Xenia_ does not like a lot of such current for example). Most corals, however do need this type of current. Good examples are Bubble coral, Elegance coral, Frogspawn and other Euphyllia corals.

Do everything that you can to maintain very low nitrate, phosphate and silicate levels. Use chemical filtration compounds to achieve these low levels if you need to. Several articles in the main library deal with algae and how to control them. You may wish to read and DL them.

Test your aquarium water and the water you add to the tank regularly to ensure that none of these levels get out of hand. You can check the water quality articles for more details on what these levels should be, in greater detail than given below:

-Nitrates between 5 and 10 ppm total nitrate. Note the word "total". It is very important in this context.
-Phosphates between 0.02 and 0.04 ppm. If they get any higher micro-algae will start to appear.
-Silicates below 0.5 ppm. Anything higher than that level will cause diatoms to grow. Some of these may attach to coral skeletons and cause damage, as explained earlier in this article (the real dangerous ones are the encrusting types of diatoms).

When a coral is infected you can try the following method:

Remove the brown slime stringy material (you can often siphon most of it out). Do this while the coral is still in the aquarium. Hold the siphon an inch or so away from the slime and start it up. Dump whatever you siphon out into a bucket. Do not reuse the water in that bucket. It is laden with elements and chemicals you do not want back in your tank, besides the slime that you removed and that you do not want in the tank either. Note that sometimes you need to siphon this off several times, hours apart or on consecutive days. Slime may reappear and needs to be removed.

Dip the affected area in fresh water for about one minute maximum. This is optional. Vitamin C treatment alone is usually all that is needed.

Clean the affected area with a real soft brush wiping any brownish material you see off the coral.

Rub some powdered Vitamin C on the affected area. Hold the coral out of the water for a minute or two.

Treat the entire tank with Vitamin C at the therapeutic dosages recommend. (more on vitamin C to follow)

Keep treating the tank with vitamin C for at least 14 days. This is most important if you want to achieve the results you need to achieve: healing of the coral and eventual regrowth of the polyp in most cases.
Aim good and strong water current at the coral's affected area so it does not become reinfected. There are no guarantees but, the use of Vitamin C will, in the majority of cases, prevent reinfection based on my long time experience with using C in high dosages.

Of course, in addition to all of the above make sure that you improve the water quality in your tank. This is one of the most important matters to take care of, second only to the use of Vitamin C.

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