Diseases in the Aquarium - Part IV
A nearly complete guide to Fish Diseases

An Article by George J. Reclos

DISEASE FUNGAL - caused by several members of class Phycomycetes the best known of which is Ichthyophonus (=Ichthyosporidium) hoferi. May be regarded as a time- bomb ticking away in ALL fishes which lays dormant whilst the fish is not under stress. Should conditions in the system deteriorate the fungus suddenly explodes into action and the fish may die.
SYMPTOMS Rapid loss of body weight - often despite good appetite, leading to vertigo (loss of balance) and abnormal swimming pattern. Some of these symptoms can be confused with same symptoms produced by physical or pressure damage to swim- bladder. Early symptoms later deteriorate to ulceration and fin damage probably as a result of secondary bacterial infections on damage sites caused by loss of balance. Finally if untreated, the spleen, liver kidneys and brain become infected, "Pop-eye" develops and in the last few hours, breathing rate increases significantly.
TREATMENT "Spring clean" the entire tank. Treat water with    until respiratory rate falls to normal. Stop all feeding until symptoms disappear.
PREVENTION These diseases are extremely difficult to treat - no doubt due to the facts that:

a) they are essentially diseases of the internal organs i.e. spleen, brain, liver, etc., which are difficult to reach with medications, and,
b) apart from Saprolegnia, there are no easily-seen external symptoms until the disease is already well advanced.

The key to successful avoidance however is undoubtedly keeping the system scrupulously clean at all times. Never overfeed, use the Nitrate, Nitrite, Ammonia, pH and Hardness test kits to ensure that water management, and water chemistry are always maintained within optimal limits. In short - keep stress to a minimum so that the time bomb ticks quietly away until your fishes cheat it by dying of old age.

Leech infestation
Caused by Piscicola geometra and various other leeches.
SYMPTOMS Large leeches, measuring up to 5 cm (2 inches) long firmly attached to the skin, fins and, perhaps, gills. Heavily infected fish may appear listless, thin and occasionally behave in an agitated fashion. Reddened areas on the fish body indicate previous points of attachment which are susceptible to secondary fungal infections.
TREATMENT Organophosphorus insecticides such as metriphonate may be used (0.25-0.4 mg / liter, continuous bath for 7-10 days, may need repeated). Since this medication will kill the leeches but may not affect the eggs a combined therapy should be used.
PREVENTION Avoid plants from doubtful sources.

Lernea (see Anchor Worm)
Lice (
see Argulis

DISEASE LYMPHOCYSTIS - caused by a virus (first ever described in fishes - 1965) which gains entry to cell through rough handling or fighting.
SYMPTOMS Large, (1-5mm) off white granular growths - often spherical and attached to any part of body or fins. Very rare in f/w fishes. Fish shows little signs of distress and often continues feeding normally. Surface appearance of cyst resembles small ball of cauliflower or raspberry. No increase in breathing rate is detectable.
TREATMENT Remove tumors surgically with a scalpel or razor-blade and sterilize area before returning fish to aquarium. Feed as normal. Surgically removed lymphocystis may recur.
PREVENTION The Lymphocystis virus is present in almost all bodies of seawater and brackish water, so that any fish which suffer physical damage to body or fins may become infected. MORAL - handle fishes very carefully and prevent aggression amongst tank members. It is extremely rare for this disease to prove fatal as a primary cause.

Malawi bloat (bacterial disease - gram negative)
DISEASE Causal pathogen(s) not certain - possibly multiple fungal/bacterial or viral infection. It could be due to a metabolic or nutritional disorder.
SYMPTOMS Fish's body bloats out (as though full of roe) and, viewed from above, scales stand away from body producing a pineapple-like appearance - most common in Carp family and Anabantids. Long, pale faecal casts. Ulcers on body, pale gills and a "pop eye" appearance are also common.
TREATMENT As soon as abdominal swelling is noted, isolate the fish and treat with a broad spectrum antibiotic. Early treatment is essential. You could use oxytetracycline (20-100 mg/ liter; five days bath, may need repeating), tetracycline hydrochloride (40-100 mg/ liter; five days bath, may need repeating) or minocycline hydrochloride. For minocycline we recommend 250mg/10 gallons of water. On day 2 change all the water and add the medicine again at the same dose for another 2 days. Increase aeration during treatment. Do not use minocycline a third time in a raw. Caution: tetracyclines are photo sensitive - turn lights off during treatment - better still cover the whole tank with a blanket. If the fish is still eating, soak the food in a concentrated solution of the antibiotic before feeding.
PREVENTION Avoid overfeeding or feeding the wrong kind of food (e.g. vegetable matters to carnivores).

DISEASE Caused by free living animals
SYMPTOMS Such animals appear to suddenly "bloom" in an aquarium. Tiny mites (less than a millimeter in size) may appear from time to time in the damp area between the water surface and the cover glass.
TREATMENT None effective but prevention is effective. Mites can be collected and removed from the surface damp cloth.
PREVENTION Do not overfeed, regularly maintain the filter and clean the gravel often.

Mouth Fungus
DISEASE - MOUTH FUNGUS Caused by Chondrococcus columnaris bacteria.
SYMPTOMS Greyish-white cotton wool like growths around mouth area.
TREATMENT In a soft, acid water aquarium, improve the water quality and decrease bacteria-count with acidifying agents. Use a proprietary antibacterial agent which may also be applied topically. Increase aeration and filtration to maximum acceptable level.
a) By regular usage of sensitive Ammonia, Nitrite and Nitrate test kits, so regulate the amount of feeding to ensure that free ammonia/nitrite NEVER appear in your aquasystem. With correctly designed filtration system, ammonia, nitrite and nitrates should never be allowed to climb above minimal levels.
b) Never overfeed:
c) Never use "spoiled" foods:
d) Never use sea foods, Daphnia, Tubifex etc., which have not been gamma-ray irradiated:
e) Always quarantine doubtful looking fish in a general antibacterial remedy
f) ALWAYS prevent vitamin deficiency in captive fishes by adding vitamins

To summarize the above in a few words, what one is really saying is:- Disease in fishes, as in all creatures, is always an inevitable response to STRESS EXPOSURE. Stress in the aquatic enviroment can assume many forms, i.e. chemical (=pH, nitrogeneous toxins), physical (=temp., S.G., oxygen tension), biological (=poor feeding, vitamin deficiency, etc.), psychological (=aggression, clumsy handling). Avoid stress = no disease.

Neon tetra disease (bacterial disease - gram negative)
DISEASE Neon tetra disease - caused by the microsporidian parasite Pleistophora.
SYMPTOMS Neon Tetra, (and rarely other tetras, zebra danio and some barbs) begin to lose normal brilliant, sharply demarked coloration - especially the red stripe; respiratory rate increases to 100 + GB / min. (gill beats per minute). Other symptoms include unusual swimming behavior, spinal curvature, emaciation and finrot.
TREATMENT No treatment has been completely effective. Some success has been achieved using furazolidone (50-75 mg/Kg fish, with food, each day for 7-10 days). Change 25% - 33% of aquarium water. Since this medication may just control the outbreak of secondary infections rather than acting directly on Pleistophora you should always isolate fish that have shown the symptoms and treat them separately. Fish that recover may still host the parasite. Avoid cannibalism of dead fish.
PREVENTION Improve aquarium hygiene and or filtration. Improve feeding regime. Never buy these species if not fully quarantined - use an antiparasitic aquarium remedy while in quarantine.

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