F r e s h w a t e r  F i s h  D i s e a s e s

This is a glossary of common diseases which infect freshwater fish. Although not every disease is treatable--or easily diagnosed, this list should serve as a basic aid in diagnosing and treating ailments.

Here is a list of common freshwater diseases.

Ammonia Poisoning


Symptoms: Red or bleeding gills. Fish may appear darker in color and may gasp for air at the surface.

Treatment:Ammonia Poisoning can be prevented but is impossible to cure. Avoid adding expensive fish to new tanks. New tanks must sit for two to four weeks until the bacterial level is sufficient to handle the tank load; add a few inexpensive fish at this time. Purchase an ammonia and nitrite test kit. Test the water until the ammonia drops to nearly zero. At this time, you should notice an increase in the nitrite level. When the nitrites are gone, it will be safe to add fish. Note that the bacterial phases will not take place unless the tank is initially stocked with feeder fish which can be removed after treatment. For larger biological loads, purchase a wet/dry filter (marine only) or a freshwater biological filter such as the Penguin Bio-Wheel by Marineland. For the immediate removal of ammonia, purchase an ammonia detoxifier such as Kordon's Amquel. However, it is best left alone until the bacterial load is sufficient.

Information: Ammonia Poisoning is common in new aquariums, especially when immediately stocked to full capacity. Ideally, the level of ammonia should be zero. Although trace amounts are generally harmless, they can still lead to problems over time. Understanding the nitrogen cycle is essential for the keeping of any aquatic life. In essence, try to maintain your aquarium with no traceable ammonia present. The amount of ammonia present is usually accompanied by a rise in pH. As ammonia is a strong base, it is stabilized by alkaline water. It can cause damage to the gills at a level as small as 0.25 mg/l.


External Bacterial Infection


Symptoms: There are a great deal of possible symptoms associated with this disorder. There may be spots on the body which appear red or orange. Watch for red streaks on the surface on the body. Dropsy (bloating) is also a sign of a bacterial disorder. "False Fungal Infections" look like fungus but is actually a bacterial infection known as Columnaris. These symptoms may include a white or gray film on the body.

Treatment: There are a number of effective treatments for many stains of bacterial infections. Three of the most common are tetracycline, penicillin and naladixic acid. Salt baths are another effective treatment.

Information: Bacterial infections are often difficult to diagnose due to the many different types. Orange or red streaks on the body is usually the only fool-proof method for the determination of a bacterial infection.


Black Spot


Symptoms: Small black specks on the body.

Treatment: Black spot is generally easy to cure. There are a number of commercially available treatments and preventatives.

Information: Black Spot, or diplopstomiasis, often follows the addition of new aquarium fish. All fish are susceptible, especially the Silver Dollar and Piranha. It is fairly easy to diagnose and treat.




Symptoms: White or gray material covering the eyes only.

Treatment: As far as I know, the only treatment specifically designed for this ailment is Eye Fungex by Aquatronics. In the process, special attention should be made to assure that ammonia and nitrite levels stay within accepted measures.

Information: Cataracts are fungal growths on the eyes. Treatment with any aquarium fungicide should work. Its probability increases with water rich in ammonia or nitrates.




Symptoms: Bulging eyes

Treatment: There are a few commercially available products which treat corneybacteriosis. Penicillin and tetracycline are among them.

Information: Corneybacteria causes swelling in the head which will push the eyes outward. It is caused by overcrowding and water of poor quality, having an excess of ammonia and / or nitrites.




Symptoms: Bulging sides and stomach. Scales may be forced outward.

Treatment: See Internal Bacterial Infections

Information: Dropsy is not a disease. It is, however, a sign of an internal bacterial infection. It is so often a symptom of bacterial infections that it has been classified separately.


Fungal Infections


Symptoms: White or cotton-like substance concentrated mainly on scrapes, surface injuries, fins or mouth.

Treatment: Treatment of fungal infections is relatively easy. There are a great many commercially available products for this, including MarOxy by Mardel Laboratories and Super Sulfa  by Aquatronics.

Information: This is a very common disorder which infects all kinds of tropical fish. It is intensified greatly with fish having damaged fins or cuts and scrapes. It is also much more likely in poor water conditions in which there are unacceptable levels of ammonia or nitrites. Fungal infections are also a sign of bullying by other fish. Fin nippers will damage the fins of other fish making them more susceptible to fungal infections and external bacterial infections such as fin and tail rot.


Ich (Ichthyophthiriasis)


Symptoms: Small white pimples concentrated mainly on the fins. Pimples look like granules of salt.

Treatment: Treatment of Ich can be difficult. There are several medications and preventatives available including Super Ich by Aquatronics and Maracyn and Maracyn-Two by Mardel Laboratories.

Information: This is the most widespread and common freshwater fish disease. The small pustules are actually sacks of tiny protazoans. In a few days, the sacks break open and the parasites fall into the aquarium gravel where they multiply in great numbers. When mature, the new protazoans attack the rest of the fish. It is this lifecycle that makes Ich so contagious. The protazoans will weaken the fish progressively by destroying the protective coating.

The protazoans may only be destroyed after they have left the sacks. When embedded in the aquarium gravel, they are susceptible to medication. Therefore, increasing the temperature of the water during treatment can speed up the life cycle, causing the pustules to break open quicker. After exposed, the protazoans are killed before they can multiply.


Internal Bacterial Infection


Symptoms: One of the most common symptoms is Dropsy. The body may be enlarged in various areas.

Treatment: Treatment is relatively easy. There are a number of medications available such as penicillin, tetracycline and naladixic acid.

Information: There are many different types of internal bacterial infections. However, they are relatively easy to cure.




Symptoms: Symptoms may include black patches on the body and fins. The body may become bloated or swollen in some areas.

Treatment: As far as I know, there is only one medication designed specifically for myxobacteriosis--Phenocide by Aquatronics.

Information: This infection is rather uncommon but fairly easy to treat. Its probability is intensified by overcrowding and poor water quality with high levels of ammonia and / or nitrites.




Symptoms: Very small white speckles on fish. Resembles a fine powder.

Treatment: There are many commercially available products to cure Velvet. Among them are Maracide by Mardel Laboratories and Super Velvet by Aquatronics.

Information: Velvet, or Oodinium, is a very common disease which resembles Ich. The white pustules are much finer and are located mainly on the body. It is a little easier to cure than Ich, since the life cycle is not so rapid. It commonly follows chilling or stress caused by transportation or poor water quality.


Parasitic Infestation


Symptoms: Visible worms, flukes or lice on the body.

Treatment: Pick the visible parasites from the fish. Follow with commercially available treatment such as Aquatronic's Diacide or CopperSafe by Mardel Laboratories.

Information: Parasitic infestation is perhaps the easiest to diagnose. The fish must be removed from the tank while the parasite is removed. Follow up treatment is essential to prevent fungal or bacterial growth.


Home ] Disease Diagnosis ] [ Freshwater Disease Charts ] Saltwater Disease Charts ] Medications ] Treatment and Methodology ]

Copyright 2006 @[Versaquatics]. All Rights Reserved.  Created and edited by VersAquatics Co USA.