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.

Get our free betta illness guide

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. An aquarium with inadequate water conditions is usually the cause Popeye, in most cases but not all.

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.

Popeye is usually a bacterial infection. We also recommend reading our page on bacterial infections.

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.

How to treat betta popeye

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:

Kanaplex by Seachem is a healthy option for bettas and contains Kanamycin — view it here on Amazon.

1. Do a 90% water change. Get your betta into clean, healthy water. Change the aquarium water 90% every 3 days.

2. Add any Kanamycin to the aquarium.

3. Make sure the medicine properly dissolves into the water, stir if need be.

4. Be sure to add Kanamycin again when doing a 90% water change.

If the Popeye heals before 3 days do not continue with the treatment.

Erythromycin by API

If Kanamycin does not seem to cure your betta's Popeye after 3 days switch to Erythromycin and follow the steps above again — you can buy it here from Incredible Pets.