Betta with swollen gill.


New Member
Aug 15, 2022
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I've owned fish for a good 10 or so years and got back into bettas about 1 or 2 years ago and I've finally got the understanding for betta keeping I wish I had when I started fish keeping. Recently my betta fox has gotten a swollen gill that looks extra "scaley", I was hoping someone else could help me correctly identify what is actually going on in his gill. (Hoping it's not tumors)

He eats perfectly fine, very interactive, well fed and is easily constipated (i do a regular fasting day each week to try to help him out).


Fish Guru
Jan 26, 2008
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Perth, WA
bit hard to tell from the pictures but it's either a tumour or infection. There's no cure for a tumour. You can try salt for 2 weeks and it might help it it's an infection. If it doesn't, then it's probably a tumour.

You can add rock salt (often sold as aquarium salt) or swimming pool salt to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria, fish, plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.

When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes

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