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My betta fish has a strange lump, but seems healthy. What's wrong?

Updated on September 23rd, 2025

Pet's info: Fish | Betta | Male

I noticed my roundtailed betta fish has this strange lump/bump/spot on him. His tank is at the optimum environmental levels, he swims and eats without problems. I'm new to having a betta fish, so I'm not not sure what this kind of spot means. Hopefully the pictures will attach this time.

4 Answers

Most Helpful Answer

Answered By Todd Cecil

Veterinarian

Published on February 20th, 2020

Thanks for reaching out about Spike and including a photo. It is difficult to visualized the lump on the picture but if water quality is pristine, a veterinary visit might be in order to assess. Bumps/lumps can be parasites, infections, enlarged internal organs and more. Monitor appetite. Containers of food should be re-purchased every -23 months as vitamin C degrades quickly and fish has a nutritional requirement for vitamin C. If not a new fish (owned for several months or more), unlikely to be parasitic problem.
Good luck.

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Dr. Massimo Orioles, DVM, Cert AVP, MRCVS
Veterinarian
Published on June 6th, 2018
Even though a picture would help to determine specifically the underlying cause, these kind of lumps/growths need to be ideally assessed by your veterinarian to have a definitive and specific answer. Usually there are two ways your vet can do that a part from examining it directly during physical examination. A biopsy can be taken under local or general anesthetic, otherwise a smaller sample through a fine needle can be aspirated (this technique is called FNA= fine needle aspiration).
Differentials include skin cysts, infections, benign or more sinister type of tumors.
Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.

1Pet Parents found this answer helpful
Answered By Todd Cecil
Veterinarian
Published on August 10th, 2019
Thanks for reaching out about Raju and including photos. Looks like his spine is curved, this could be an injury, vitamin C deficiency (scurvy) or other. Test and correct water quality. A veterinary visit is needed to assess and a radiograph might be recommended. The swelling could be due to the proposed spinal changes but also an abdominal mass or fluid build accumulation. An aquatic veterinarian should be able to assist with this also.
Good luck.
1Pet Parents found this answer helpful
Answered By Angel Alvarado, LVT
Licensed Veterinary Technician
Published on April 22nd, 2018
It may be local infection or something he was born with. Keep an eye on it for rapid change or growth. Monitor him for lethargy or loss of appetite. Maintain pristine water quality and it may resolve on its own.
1Pet Parents found this answer helpful

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My Betta fish has a bump on its head. What is it and how to treat?

Without an image or exam, it is difficult to say with any certainty what the lump may be. Infection or injury would be likely culprits. If he has anything sharp in his bowl, remove it. Check the water quality and chemistry as poor water quality can predispose him to infection. Use a home test kit or submit a water sample for testing. Most pet stores will do this for free or for a small fee. Aim for 0 ppm ammonia and nitrites with a nitrate level of 20 ppm or less. Partial water changes can be done to stabilize chemistry and improve water quality. Use only aged or conditioned water that is temperature matched to prevent stress or shock. Bettas do best between 78 F and 80 F. Change no more than 30% total volume at one time. You can try using plain aquarium salt (NOT table or Epsom salt) as a general tonic. It can treat minor infection and helps aid in recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup of tank water and gently pour it into the tank. Treat for 10-14 days then reassess his condition. Perform water changes afterwards to reduce salinity. Do not use salt for more than 14 days in a row. If there is no change, a broad spectrum antibiotic 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.

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My betta fish has a growing lump on its side. How can I treat it?

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Why is my betta fish sick with a chin lump and struggling to swim?

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What causes a lump under my Betta fish's chin and how to treat it?

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My fish has a bump on its head. Is it serious? What should I do?

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My betta fish has a small ball on its bottom fin. What is it?

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Why is my betta sick, lethargic, and has white spots? What can I do?

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