My betta fish has a growing lump on its side. How can I treat it?
Updated On September 23rd, 2025
Pet's info: Fish | Betta | Male | 2 years and 3 months old | 0.06 lbs
hi! my betta fish has had a lump on his side for about 10 days, and it seems to be growing. i’ve tried salt baths but nothing has seemed to work. i also don’t live near any fish vets or, vets in general. i’ll send some pictures, and you can see the growth in them. the bump has become more stretched out and lighter.
3 Answers
Most Helpful Answer
Published on August 23rd, 2019
It may be a tumor or infection since it is just on one side. Without diagnostics though, it can be difficult to determine the underlying cause. Maintain pristine water quality via filtration and regular partial water changes. You can try a broad spectrum antibiotic which can be found in the aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated. If antibiotics to not resolve the lump, then it could be a tumor or mass which would need to be addressed by a veterinarian experienced in treating aquatics.
12Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on June 20th, 2017
It is likely not his swim bladder since that is an internal organ. Fungal infections appears as fuzzy growths on fins and scales. A tumor would appear much more solid than a fungal infection. Fungal infections can be treated using an antifungal medication which can be purchased online or in the aquarium section of most pet stores. A tumor could be removed, but you would need to have a veterinarian experienced in treating fish examined it first. Check the water quality and make adjustments as needed. Confirm proper temperature (78-80F). Monitor the lump for rapid change or growth.
4Pet Parents found this answer helpful
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Published on June 16th, 2020
Without seeing her myself it is hard to say what the lump is. It could be an abscess, an ulcer or a tumor. There are other causes of lumps that may be mistaken for tumors including: fluid retention, swim bladder disease, and constipation. If the lump is white, then yes, it is most likely an abscess. You can try this product but typically it will need to burst on it's own. You need to be very diligent about keeping the water clean. You can refer to the article below: https://www.amazon.com/dp/B06XDFJ5XN?tag=bettasourcesite-20 https://bettasource.com/betta-fish-tumor/
1Pet Parents found this answer helpful
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