Betta Body Rot

Body Rot is easily confused with Fin Rot because they share similar names.


The fact of the matter is they are quite different. Fin rot is caused by a bacteria called “Pseudomonas” and is an external primary disease caused by stress and poor water conditions. Body rot is caused by a bacteria called “Aeromonas” and is internal rather than external. This makes it much harder to diagnose. It is also a secondary disease meaning it primarily occurs in the presence of illness.

Luckily both fin rot and body rot are gram-negative, rod-shaped, bacteria meaning they can be treated with the same medications. This helps if you are unsure of which bacteria is infecting your betta fish and whether or not you are dealing with both types at once. To read more on fin rot, click here: Betta Fin Rot


Body Rot – Aeromonas


betta body rot

(click to enlarge)

Body rot is caused by a bacteria called Aeromonas which is a negative-gram, rod-shaped bacteria. Body rot is a secondary condition, meaning it infects only sick betta fish. Aeromonas very rarely infects healthy fish. This is because Aeromonas is always present in your tank and will only infect your fish when its health has already been compromised. However, in rare cases, it can be a primary infection caused by the consumption of tainted food.

What causes body rot? When stress and poor water conditions exist in a betta’s environment, the immune system weakens and mucus lining thins. This leads to stress and illness in your betta fish. Aeromonas waits for the perfect opportunity to jump in and join the party once a disease has set in. The bacteria will get into the blood stream and travel to the first organ it can find to infect. It releases Aerolysin Cytotoxic enteroToxins(ACT) which causes inflammation and hemorrhaging.


So how will you know if your betta fish has body rot?


betta fin body rot

(click to enlarge)

A body rot infection can be hard to diagnose because the infection is primarily internal and there are many different species of Aeromonas. However the most common symptoms are ulcers, hemorrhaging around the gills or at the base of fins. fin rot, swollen abdomen, protruding eyes and scale loss.


Treatment of Body Rot


It is important to know that this disease is immune to many antibiotics and water conditions which includes varying temperatures. An immediate water change(click here for bowls: water change) is crucial and the treatment of underlying conditions. Once you have your betta bowl(or aquarium) water stable you must treat your betta fish for any primary diseases. This would be likely to include a parasitic infestation. Once you have pin pointed the original disease and have completed treatment, your betta should be able to recover. If not you can treat the actual body rot itself. Tetracycline would be best especially if fin rot or any other bacteria is apparent.




It is important to remember to keep up with regular maintenance to keep your betta healthy. Quality water conditions will prevent many diseases and keep your betta’s immune system running efficiently. Water changes can be tedious when you are first starting out. Once you get into the habit of performing water changes and testing regularly it will quickly become a normal routine for you.

Here are some resources to help you out:

Clean a Betta Bowl in 5 Easy Steps

How to Clean an Aquarium in 5 Steps

Also you can keep your betta’s water at about 82 degrees and add a light amount of aquarium salt on a regular basis. I follow this and have not seen fin or body rot infect my bettas or aquarium fish since 2008. Do not think of the salt as making the water being “salty”. Think of it being soft. That is why we have water softeners in our homes and fill them regularly with salt and yet when we drink we do not taste the salt. Unless you put too much in of course.

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