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COMMON FRESHWATER DISEASES: Their identification and cure

   When examining common fresh water fish diseases, we must look at three important factors: identification, cure, and also cause, since as the old adage goes, "An ounce of prevention is worth a pound of cure." 


Observations: Gray or white lesions on mouth or caudal area, deterioration of fins. 

Conditions: Caused by overcrowding, poor filtration and resultant high ammonia and bacteria levels, lack of minerals (food). 

Fish Affected: Occurs most on fancy guppies, sailfin mollies and all other live-bearers. 

Cure: Kanamycin and Nitrofurazone (Any broad spectrum antibiotic can be effective) 


Observations: Balls of fungus, usually located on dorsal and/or pectoral spines. 

Conditions: Epistylus grows on gravel and moves onto fish with injured spines. 

Fish Affected: Corydoras, Pimelodellas, any armored catfish, and iridescent sharks are especially prone, although it can occur in any fish with injured spines. 

Cure: A combination of malachite green and formaldehyde, plus the actual removal of fungus balls to speed recovery. 

Fin and Tail Rot 

Observations: Deterioration of tail and/or other fins. 

Conditions: High ammonia or high bacteria levels. 

Fish Affected: All fish, but most often on live-bearers (platies, variatus, swords, and guppies). 

Cure: Kanamycin and Nitrofurazone (Any broad spectrum antibiotic can be effective). 

Gill Disease 

Observations: Distended opercula or frayed gills. Fish may not hang at top, but will be gasping or breathing heavily. 

Conditions: Caused by overcrowding and low dissolved oxygen. 

Fish affected: Occurs in all fish. 

Cure: Kanamycin and Nitrofurazone, or a broad spectrum antibiotic. Use Dylox for secondary fluke infestation. 


Observations: Blood in fins or body which is visible to the eye. 

Conditions: Drop in temperature and poor water quality. 

Fish Affected: All, but especially new fish. 

Cure: Kanamycin and Nitrofurazone or any good broad range antibiotic. 

"Ich" (Ichthyoptherius) 

Observations: White spots on fish's body. 

Conditions: Rapid temperature change, pH fluctuation, and ammonia increases; also caused by poor water quality. 

Fish Affected: All fish; most vulnerable are clown loaches, Pimelodella pictus (angellicus), hatchetfish and wild caught silver dollars. 

Cure: General Ich medications (malachite green). Warm temperatures and at least one teaspoon of salt per gallon of water increases effectiveness. Scaleless fish can tolerate only one half the recommended dosage. 

Neon Tetra Disease 

Observations: A washed out appearance in color, small white patches, usually near the dorsal area, and/or swimming behavior abnormalities. As with other types of fish, dying Neons usually turn darker in color. 

Conditions: Unclear- may be a combination of several diseases, or bacillus bacteria. Outbreaks occur in stressful situations, temperature changes, and with water quality problems. 

Fish Affected: Neon Tetras 

Cure: A combination of Nitrofurazone and Acriflavine has some success, and formaldehyde has been moderately effective in stopping its spread. 


Observations: Similar in appearance to Epistylus, and often the two are confused. 

Conditions: Saprolegnia is a true fungus. It is an opportunistic organism, attacking any traumatized area. Also a common cause of fish egg destruction. Not strictly parasitic, Saprolegnia can be found growing on any decaying organic matter 

Fish affected: Any fish with open wounds or necrotic areas of bacterial infection. 

Cure: Potassium permanganate at the rate of one gram per one hundred liters of water for ninety minutes. There are also commercial products which may be used in an aquarium. Cleanliness is of utmost importance as well as treatment of the underlying disease which started the problem. 


Observations: Rocking back and forth. 

Conditions: Change in water temperature and poor water quality. 

Fish Affected: Gouramies and sailfin mollies. 

Cure: Malachite and Formaldehyde.


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