I intend looking at two fish problems. These two problems are probably the most feared by marine aquarists. Those who keep a [tag-self]fish only aquarium[/tag-self] could sweat a little less, but the owner of a [tag-self]reef aquarium[/tag-self] can have real trouble.
The first is the so-called marine [tag-self]white spot[/tag-self], or ‘[tag-self]ich[/tag-self]’. The cause of this problem is Cyptocaryon irritans, which is a parasite. The second is [tag-self]marine velvet[/tag-self], caused by the parasite Oodinium ocellatum. On the wild reef it is possible that a fish may run into one or other of these parasites once or twice, or perhaps never. The parasitic attack will not amount to much on the wild reef because of the enormous amount of gallonage and the very large numbers of fish present. In the confines of an aquarium it is a different story – this is why.
Though there are comparatively few fish in the aquarium, per gallon there are usually a lot, particularly in a fish only system. Also the parasites are restricted to the gallons and fish available, which is obvious, but it is that which causes the major problem.
The major problem is caused by the reproductive cycle of the parasites. If a fish is introduced to the aquarium with just one parasite attached to the outer body, this is enough. The parasite usually stays on the body of the fish for one or two days with white spot, three or four days with velvet, then it encysts and falls off. It drops to the bottom or on to rocks and begins to divide into many more parasites, and this process can last for up to two weeks. The parasites then reach the free swimming stage, when they search for a new host fish. A new host must be found within about 48 hours or the parasite will die. In the confines of the aquarium a fish or more will be found. The process then begins all over again. In due course, fish can become covered in parasites which continue their reproductive cycle. Eventually, the fish are so infested they die. Then the parasites will die too, but it is too late.
How are the problems recognised? First, fortunately white spot is fairly easy to see. The fish may ’scratch’ against rocks and may have one or two or more little white pimples anywhere on the body or fins. The spots are somewhere near the size of a pinhead.
If a pimple is seen then do not immediately assume that it is white spot. Observe if it goes away as sometimes a ’pimple’ is seen that is not white spot. However, watch very carefully for any development.
Velvet is more difficult to see. Again, the fish may ‘scratch’ against rocks. It is more likely that its gill beat (respiration) will be faster. It may hold its fins closed against the body. Note that the above symptoms may or may not be present. What are looked for on the body or fins of the fish are yellowish or white/grey spots. Unfortunately, these spots are very small and can hardly be seen. Try looking at the darker coloured areas of the fish. If a fish gives the chance, use a magnifying glass. Also, the aquarist can attempt to view the fish looking directly at the head when the fish’s body is behind the head (ie. head-on) – looking down the length of the fish the tiny spots might more easily be seen – the fish could appear to have a ‘dusting’. Velvet is the more deadly of the two problems, to a large extent because of the difficulty in identifying it.
With both problems, careful observation, consideration, and action are imperative. Failure to diagnose the presence of the parasites can lead to severe problems, at the worst all fish being badly infected and many or all facing death.
If the spots are parasites, then proper treatment must be given promptly. The headline rule is: “Don‘t Panic” When the spots are diagnosed, they do not develop so quickly that care cannot be taken.
If the aquarist has a fish only aquarium, then the best thing is to deal with all the fish as a safety measure. Dealing with just the fish showing a problem using a quarantine tank will not deal with any parasites that are in the aquarium, either in the division stage or unnoticed on another fish. All the fish can be moved to a quarantine tank if desired. They will have to stay in quarantine for at least two weeks, to try to ensure that any parasites in the display aquarium that are coming out of the divisional stage or swimming are dead as they couldn’t find a host. Whatever aquarium is used, the first action is to consider UV treatment of the display aquarium. If UV equipment is not held, then it is not absolutely necessary to buy a unit. UV will help destroy the parasites in their free swimming stage, but removal of all parasites is not guaranteed, and UV does nothing to parasites that are on a fish or encysted.
The use of a copper treatment will destroy the parasites. Warning: copper is deadly to
invertebrates. Do not use copper if invertebrates are present or it is intended to introduce any in the future. Stick strictly to the manufacturer’s recommendations about copper dosage and exposure time, and ensure there is a good copper concentration test kit available.
If invertebrates are a problem then see the reef system comments below. Invertebrates will be fine, of course, if they remain in the display aquarium when treatment is done in a quarantine tank. Obviously, ensure water is not transferred from the quarantine to the display aquarium.
When treatment is over and hopefully successful, and when the treatment was in the display aquarium, use a power filter and put activated carbon in. This will take out remaining copper. Throw away the water in a quarantine aquarium – do a larger (say 25%) water change in the display aquarium.
Keep a close eye on the fish to make sure all is well.
If the aquarist has a reef aquarium, then it is clear there will be livestock present that prohibits the use of copper. As above, if a UV unit is available, activate it immediately. Consider treating the fish in a quarantine aquarium also as above. It will be more difficult catching the fish as they are going to hide in the rockwork, and the aquarist will not be keen to dismantle the reef. If it is clear the fish cannot be successfully caught, then the option is to use a reef safe treatment.
Reef safe treatments have not been shown (to my knowledge) to be as effective as copper. Even though they are termed ‘reef safe’, the manufacturer’s instructions must be strictly adhered to. It is possible that in the treatment process some corals close up because of contact with the substance, or certain types of livestock must not be present.
Once treatment has ceased activated carbon should be introduced to clean up any treatment residue, subject to the instructions that came with the treatment. A larger than normal water change is also beneficial.
There are other treatments that can be used on infected fish other than described, but these require capture of the fish and removal from the display area, so the reef aquarist faces the same problem.
The best way to avoid problems such as described above is to purchase fish with great care, and introduce them with the same care. Stress is a large factor that can cause problems because of impaired immunity. The use of a quarantine aquarium is very sensible.
To end on a positive note, and assuming that fish are carefully introduced, the chance of problems as described are reduced nowadays. The greater knowledge and practice of wild capture techniques, better transportation of fish, and more knowledgeable retail shops means purchasing a healthy fish is more likely. The aquarist is the final guard however, and must never lower the defences: careful selection, careful introduction, careful ongoing observation, stress avoidance at all times, proper nutrition, and overall high class husbandry which includes high quality seawater.