Wednesday, October 6, 2010

Primer on Common Marine Fish Illnesses

We've gone over how to do a freshwater dip and how to set up a hospital tank. But what about the meat and potatoes? What does a sick fish look like? What diseases do fish get, and how do we get rid of them?

A sick fish displays obvious changes in normal behavior. Erratic swimming patterns, listless behavior, lying on its side, dull or pale color, loss of appetite, rapid breathing, and white, fluffy patches on skin, gills, or body, all of these are signs of a sick fish. The earlier you spot the symptoms, the better a chance you have of successfully treating and healing your fish!

Why do fish get sick?
Stress. Simple as that. Stress weakens the immune system making the fish more susceptible to disease. Stress comes in many forms including:
1. Shipping and transport.
2. Introduction to a new tank.
3. Poor water quality or sudden changes in water parameters (salinity, pH, temperature, calcium, alkalinity, ammonia, nitrites, nitrates).
4. Poor nutrition (not feeding enough or the right kind of food).
5. Boistorous, aggressive tankmates.
6. Poor enivronment, e.g. tank too small to meet space requirements of fish.

Common Fish Illnesses:
1. Cryptocaryon irritans (Ich)

This is an obligate parasite (meaning it cannot survive without its host) with a complex life cycle often introduced from new fish, coral, or live rock. ) (It's actually a ciliated protozoan). Tangs and surgeonfish are particularly susceptible. Death can result in a few days.
Symptoms first appear as tiny, white specks on the fins, body, and gills (like salt). The fish may itch against rocks and substrate (called "flashing"). As the infection advances, the gills are compromised, and breathing is impaired, causing rapid breathing and listless behavior. Secondary bacterial infections also often occur. Some parasitic copepods can produce identical symptoms.
Although a very common disease in saltwater aquariums, it is easily treated if caught early. In addition, a cured fish often develops an immunity to recurrent infections. Hyposalinity for 4 weeks in a hospital tank is the best treatment. Other treatments such as formalin and copper are also effective but they are pretty toxic to the fish and must be used judiciously.
Ich Links:

2. Marine Velvet (Amyloodinium ocellatum).
Symptoms are similar to ich but instead of punctate white spots, the fish has more of a white powder covering its body, almost like its been dipped in powdered sugar. Caused by a parasitic algae (actually a dinoflagellate). Symptoms start off with labored breathing. Powdered spots occur later. Because it attacks the gills first, marine velvet is more serious than ich. By the time you see it, it may be too late. In addition to powdered spots and labored breathing, swimming may also be erratic. Fish may also rub against rocks and gravel. Death can occur within two days of symptoms. Hyposalinity is not effective for this parasite. Cholorquine diphosphate (also used to treat malaria!) is a good treatment (5-10 mg/l for 10 days). Metronizazole will also treat dinoflagellate infections. Copper, formalin, and freshwater dips are also common treatments. As always, these chemicals are toxic invertebrates, micro-/macro-algae, and nitrifying bacteria.

Marine Velvet Links:

3. Black Ich (Turbellarian)

Also called Tang or Surgeonfish disease because it is often seen on Yellow Tangs. Like ich but black spots instead of white. This disease is actually caused by turbellarian flatworms from Paravortex genus. This disease is not as quick-killing as Ich or Marine Velvet but needs to be treated to prevent secondary bacterial infections from occuring. Treat with freshwater dip followed by formalin bath and recovery in QT tank.

4. Brooklynella (Clownfish Disease)Worst of the parasites. Often seen in wild-caught clownfish. This is a cilliated protozoan that can reproduce asexually, spreading much faster than Ich or Marine Velvet. Attacks gills first, which makes breathing difficult. First symptoms include rapid/labored breathing, thick, excess mucous secretion, color dulling. Lethargy, loss of appetite, cloudy eyes also occurs. Toxins secreted from protozoa cause open ulcers gills and skin. Death can occur in 12 hours if not treated immediately. Remove to QT tank and perform daily baths in formalin. Other treatments, like hyposalinity, freshwater dips, or copper, are not effective.
Brookynella Links:

Most, if not all, occur as secondary infections due to another infection, poor water quality, wounds from aggression, or some other form of immune-weakening stress. Sensitive fish such as angelfish and butterflyfish are most susceptible. The type of bacteria that cause fish illnesses varies widely from Pseudomonas, to Vibrio, as well as Mycobacteria. General symptoms include bloody patches or streaks, skin ulcers, lethargy, dull color, loss of appetite, bloated belly, swollen eye (popeye), cloudy eyes, rapid breathing, or disintegrated fins (fin rot). Without treatment, fish will eventually die from infection. The best treatment is to remove fish and treat in QT with low salinity (1.012; eases stress of fish while preventing secondary parasitic infections) and wide-spectrum antibiotics (food and water). Gel Tec is an antibiotic in food form and Maracyn 2, a sulfa drug that fights gram-negative bacteria, is also a good choice. Erythomycin is also commonly used. As with all illnesses, be sure to perform frequent water changes to manually remove the bacteria from the sick fish's environment.
General Links on Bacterial Infections in Marine Fish:
Tattered, infected fins often secondary to a wound caused by nipping or fighting. Poor water quality exacerbates infection. Common bacteria that cause fin rot include: Aeromonas, Pseudomonas, and Flexibacter. Treat with antibiotics, as indicated above.
2. Popeye/Cloudy Eye
Cloudy or swollen eye which often results from infection after eye is scrathed. With frequent water changes and good water quality, infection often goes away on its own. 10% oral Baytril (enrofloxacin) is a recommended treatment in QT.

3. Vibriosis
This is one of the more aggressive bacterial infections, killing in as few as 5 days. Symptoms often include red spots or streaks on bottom of fish that can ulcerate and bleed. Other symptoms also include lethargy and loss of appetite. This bacteria attacks the GI tract. Treat as with all bacterial infections (isolate fish in QT and treat with antibiotics followed by a big water change in main tank).

4. Fish Tuberculosis
Use extreme caution as the aquarist can be infected. This infection is caused by a Mycobacteria. Symptoms include loss of appetite, lethargy, pale, ulcers, emaciation, and overall poor health. Treat in QT with erythromycin.
I covered this extensively in a previous post. Basically, it causes red or white cauliflower-like lumps on the fins and body of the fish. There is no known cure (just like the common cold) but symptoms are mild, and infection often goes away on its own with time. Use methods to boost the fish's immune system. Frequent, small feedings of rich food and ensure the water quality is pristine.

Flukes and Parasitic Copepods:
Other things that can plague your fish include parasitic flukes and parasitic copepods. Symptoms will be similar to ich (white specks, itching against rocks, excess mucous, etc.). These parasites interfere with the fish's breathing (by destroying the gill tissue). Treat with a potassium permanganate bath (10 mg/L for 20-30 minutes).
Parasitic Internal Worms:
Often caused by roundworms, tapeworms, or flukes, most fish have some type of worm infestation by the time they reach your aquarium. De-worming ( praziquantel, for instance) in a QT is highly recommended. General symptoms include dull color and slow wasting away despite increased appetite as well as the classic long stringy white poop that is often seen hanging from the fish.
Other Diseases:
Head and Lateral Line Erosion (HLLE) Disease:
This mysterious disease most commonly afflicts tangs and surgeonfish. It's cause is unknown, and there is no cure. Symptoms include discoloration and pitting of the head and lateral line. Basically, the skin or gills around this area begins to disintegrate and waste away. Poor nutrition or poor water quality is thought to contribute to causing this disease. This disease doesn't otherwise negatively affect the fish at first but, over time, can worsen and cause listlessness and lethargy in the afflicted fish.

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