This page is part of our betta disease and illness section.

We also have a handy Betta Illness Photo Guide that we send out to members of our email list. The guide includes the key points about betta illness and extra photos of symptoms.

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What is Popeye?

Most of the time, Popeye is simply a bacterial infection of the eye. A betta is not at all likely to contract it if it’s kept in a clean aquarium. A very dirty aquarium causes Popeye, in most cases.

Popeye isn’t difficult to cure, but it can sometimes be an indication that your betta has a serious internal condition. If that’s the case, then Popeye may prove fatal for your betta. Popeye is incurable if it’s a sign of a serious internal disease.

Popeye can be a symptom of betta tuberculosis. If a betta has indeed contracted tuberculosis, it won’t be long until it leads to death. Betta tuberculosis is incurable and fatal.


The main sign of Popeye is a bulging, swollen eye. The eye may also have a thick white ring around it. General reactions to illness will also occur, such as a loss of appetite and lethargy.

Possible Cures

If your betta isn’t the only inhabitant of its aquarium, it’s good practice to isolate it before treatment. Create what’s known as a quarantine or hospital aquarium so that the treatments or medicines don’t harm the other critters or plants. If any other fish also have the infection, be sure to put them in quarantine along with the betta (or even better, create a separate quarantine aquarium for each of them). If a betta has contracted popeye, other aquarium inhabitants may make the situation worse.

If caught in its early phases, betta Popeye is easy to cure and your betta should be back to normal after some basic treatment. If it’s in its advanced stages, your betta may lose an eye.

As soon as you notice that your betta has Popeye, it should be isolated from any other tank mates. If it’s the only inhabitant, the betta can remain in its current tank. We then recommend taking the following steps in order to cure Popeye:

  1. Do a 100% water change. Get your betta into clean, healthy water. Change the aquarium water 100% every 3 days.
  2. Add any Ampicillin antibiotic to the aquarium. Ampicillin usually comes in capsules and typically one capsule should be used per 10 gallons (this can vary, the additive ratio will be specified on the medication’s container). If your betta is in an aquarium less than the specified capsule per water ratio, simple break the capsule open and sprinkle a calculated percentage of the powder into the aquarium.
  3. Make sure the powder properly dissolves into the water, stir if need be.
  4. Be sure to add the powder again when doing a 100% water change.

Do not over medicate. Discontinue the treatment if no improvement is evident after a week.

Medication for Popeye

Ampicillin by Fish Chillin. (This comes in capsule form, 1 capsule per 10 gallons, so if your aquarium is 2.5 gallons, for example, you’ll only want to add a quarter of the capsule per water change).