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

An Article by George J. Reclos

Gill maggots
DISEASE Caused by the crustacean Ergasilus
Usually found attached to gills, gill covers and inside the mouth. Heavy infestations with Ergasilus can cause severe gill damage, emaciation, anemia and even death.
TREATMENT Treat the whole tank with organophosphorus insecticides such as metriphonate (0.25-0.4 mg / liter, continuous bath for 7-10 days, may need repeated). If fishes sensitive to this medication are present (e.g. piranhas), treat them separately with potassium permanganate (30 minute bath).
PREVENTION Maintain a much higher standard of aqua system hygiene, paying particular attention to filter cleanliness and avoiding overfeeding. Always stir up filter-bed before siphoning off old aquarium water when carrying out a partial water changes. Never use non-irradiated seafoods, Daphnia, Tubifex, bloodworm, mosquito etc.

Gill disease
Infection with certain fungi (such as Branchiomyces), bacteria, protozoans and monogenetic flukes (like Dactylogyrus) and / or poor water quality.
SYMPTOMS Rapid gill movements, swollen gills and discolored gill filaments with excess mucus. Fish do not eat, lie motionless in the tank or gasp at the water surface.
TREATMENT Improving the general water conditions often eases the problem. Making a prompt 30-50% water change with conditioned water is a good initial treatment. You can also add one of the aquarium antibacterial remedies.
PREVENTION Keep good water conditions and perform regular water changes.

Glochidial infestation
DISEASE Caused by the larval stages of freshwater mussels such as Unio and Anodonta.
SYMPTOMS Grey edges on the fins and / or gills are the most obvious symptoms. Can be quite pronounced in heavily infected fish.
TREATMENT No special treatment is available but luckily, this situation is not dangerous.
PREVENTION Remove adult mussels from the tank while they are shedding their glochidia (larvae) during the summer months.

Guppy disease
DISEASE Caused by the ciliate protozoan Tetrahymena
SYMPTOMS The visible symptoms are very similar to those of white spot disease.
TREATMENT A proprietary brand of white spot treatment will be effective. However, well-established infections may require several treatments.
PREVENTION Keep guppies in warm, moderately hard, alkaline water.

Gyrodactylus - body flukes (see Flukes)
Hemmorrhagic septicemia
DISEASE Caused by various bacteria, including Aeromonas, Pseudomonas and Vibrio.
SYMPTOMS Lesions, sores or ulcers on the body, reddening at the base of the fins and the vent, loss of appetite and darkening of coloration are all symptoms of infection. Ulcers may be secondarily infected with fungus. In very acute disease outbreaks, there may be very few obvious external symptoms.
TREATMENT If fish is still feeding, offer a full course of medicated food (you can soak the food in the antibiotic solution before feeding). Feed all fish in the tank with the same food. If the disease has advanced fish are likely to refrain from eating. In this case isolate the fish and treat with nifupririnol (0.1-0.2 mg/liter, continuous bath for up to 5 days, may need repeating) or, if unavailable, with antibiotics or a similar antibacterial. Larger fish may be injected with a suitable antibiotic and topical antiseptic should be applied on lesions. Adding salt may help the osmoregulation of the stressed fish.
PREVENTION Find and eliminate the causal factor.

Hexamita (Hole in the Head)
DISEASE - caused by Hexamita Protozoa parasites which are probably endemic in all populations of wild Discus species, and even in tank-bred specimens. Usually affects cichlids such as discus, angelfish, oscars and gouramis.
SYMPTOMS Small, whitish/greyish/or creamish "worms" crawl out of head region of Discus family fishes. Unless the infestation is massive and/or secondary bacterial and fungal infections develop, the condition is rarely terminal but very unsightly and may cause infestation of other fishes in system if parasites are allowed to reproduce. Hexamita often exists as a low level infection of the intestines. The onset of the disease may be due to various factors (see precention).
TREATMENT Change 25%-33% of aquarium water for treated rainwater or deionised water or tapwater (=decending order of preference). Treat with dimetridazole (5 mg/litre, continous bath) or metronidazole (7 mg/litre continuous bath). Metronidazole is not absorbed through the gills, therefore in order to be effective the fish must still be eating. In non-eating fish the drug will protect the other tankmates and eradicate the pathogen from the water column but will not treat the fastening fish.
PREVENTION Low oxygen levels, overstocked tanks, unhygienic conditions, changes in temperature and poor diet are all factors that could trigger this disease.

DISEASE Caused by the coelenterate Hydra.
SYMPTOMS Hydra have a small, stalklike body, which ends in up to ten long, slender tentacles. The tentacles have a battery of stinging cells which Hydra uses to capture its food consisting of small crustaceans, invertebrates or even small fish. Although the size of Hydra may reach a length of up to 2 cm, it can compact its body.
TREATMENT Improving the general hygiene of the tank, avoiding overfeeding and regular tank maintenance may moderate the build up of Hydras. Some species such as the three-spot gourami, and the paradisefish will consume large numbers of Hydra. Raising the temperature to 40 degrees C (after removing all the fish) is quite effective. Hydra is also sensitive to salt. A salt percentage of 0.3-0.5 % is effective to control Hydra. 
PREVENTION Improved general hygiene in the tank.

Internal Parasites (see Worms in the body cavity)

Ichthyopthirius multifilis (ICH, white spot disease)
DISEASE caused by ciliated protozoan (Cryptocaryon irritans in saltwater and Ichthyophthirius multifilis in freshwater tanks). May be caused by non - irradiated livefoods. May be accompanied by other skin and gill parasites.
SYMPTOMS Small, pure white, clearly-defined spots / cysts (about 1/4 - 1/2 diameter / approximately the size of pinhead) appear on body, gill  AND finnage. (CAUTION: do not confuse with same-sized GREYISH-WHITE, blurred-edge spots appearing on finnage only). Some cysts may join together and form irregular white patches. If untreated, spots slowly (6-24 hrs) advance to cover whole body/finnage area. Heavily infected fish may look as if they have been sprinkled with salt or sugar grains and they may scratch against rocks and gravel and show increased gill movement. Fishes do not show early sickliness and may even continue feeding lightly. Secondary bacterial infections are common. Ichtyophthirius has a direct fish-to-fish cycle and thus can build up quickly in the limited space of an aquarium.
TREATMENT Carry out a 25%-40% partial water change and treat immediately with appropriate medicine. In very hard water the treatment should be used twice daily in the early morning and late at night. Since the protozoan, while attached to the host is immune to treatment, this has to be aimed against the free swimming stages. Raising the water temperature to 32 degrees C (if the fish can tolerate it) for a few hours every 2 or 3 days may be effective. Since the disease is spread very easily it is recommended to treat the whole tank instead of individual fish.
You have to keep in mind that this disease can devastate a tank in no time. Ichthyophthiries multifilis cannot tolerate sodium chloride levels higher than 1 ppT (parts per thousand or else 100 gr / 100 liters). If your tank inhabitants don't have a problem with salt than this is the treatment of choice. I have tried it with excellent results and no losses. Since I was keeping Madagascan cichlids when the problem appeared I raised the sodium chloride concentration to 3 ppT over a period of 24 hours (1 ppT / 8 hours) and set the temperature to 31 C. I left the temperature at this level, increased aeration to its maximum and treated the tank for 15 days. You have to keep in mind that although the visual signs on your fish may vanish after 5-6 days at most (under these conditions) parasite in its free swimming stage may still be present in your tank and lead to a new cycle once you stop the treatment prematurely. I personally think that 15 days is a safe duration for this treatment.
PREVENTION It should be stated here that most workers in the field of fish pathology believe that these protozoans are present in all bodies of water and in a resting (latent) state within most fishes but only become active when fishes are exposed to stress or otherwise weakened. It is believed that the protozoan is introduced in a set up tank through new and not quarantined acquisitions. It is always wise to quarantine your fish for four weeks and use a white-spot remedy during this period. Washing newly purchased plants under running water may also protect your tanks.

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