Petco Text Logo
Petco Pet Logo

  • Two Easy Ways to Start Earning Rewards!

My fish has white growth in its mouth and can't eat. Is it Columnaris?

Updated On September 23rd, 2025

My neon tetra have developed a white growth in his mouth to the point that his entire mouth is full & he is unable to take in food. Another neon tetra has developed the growth as will & it is growing in size. The other one is bloated. I have tried a few different medications for bacteri and fungus, nothing is working. My 4 glo fish & 3 neon tetras have been in the treatment tank at Petsmart since 2/12/28 & the issues have not subsided. I am in desperate need of your help, please :(

This question includes photos that may contain sensitive content. Click to view.

View more to consider that the photos may include sensitive content.

2 Answers

Most Helpful Answer

Image profile

Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on February 23rd, 2018

It could be Columnaris, aka cottonmouth. It looks like a fungal infection but is actually an infection caused by a gram negative bacteria. You can treat with kanamycin and nitrofuran. Both are antibiotics effective against this bacteria. Brand names are Kanaplex (by SeaChem) and Furan 2 (by API). You can find them online or in the aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if necessary. You will likely need to treat the entire tank since more than one fish is symptomatic.

Vote icon

1Pet Parents found this answer helpful

Other Answers

  • Image profile

    Answered By Dr. Massimo Orioles, DVM, Cert AVP, MRCVS

    Veterinarian

    Published on

    Although from the picture it is not easy to see the actual lesions, this problem could be compatible with a bacterial infection. The antibiotic previously suggested are a good choice of treatment. Please follow strictly the labels’ instructions. A part from antibiotics, it would be good to analyse the water as well, to see if there are major imbalances that could have triggered the infection. This could be done by your local pet store for a nominal fee. If water quality is not properly maintained, antibiotics will not be effective and bacterias will keep spreading.

    Vote icon

    0Pet Parents found this answer helpful

See More Answers

Related Questions

Petco Pet Education Center
Health & Wellbeing
What fish dog food helps dry skin if my dog eats Science Diet?
Is your dog's dry skin a concern? A certified vet offers expert advice on finding the best fish-based dog food alternatives to Science Diet for essential oils.
Updated on February 04, 2026
Petco Pet Education Center
Food & Nutrition
Can chickens eat bell peppers daily and what about veggie salads?
Can your chickens eat bell peppers and salads? Veterinarian Dr. Elizabeth offers expert advice on safe feeding, frequency, and how fresh veggies boost vibrant yolks.
Updated on December 04, 2025
Petco Pet Education Center
Food & Nutrition
Is Purina Layer Pellets good for chickens? What other feeds exist?
Is Purina Layer Pellets the right choice for your flock? Get expert advice from a Petco veterinarian on Purina and other top chicken feed brands for your chickens.
Updated on December 04, 2025
Petco Pet Education Center
Food & Nutrition
My mice eat all their food together from one bowl. Is this normal?
Do your mice quickly eat together from one bowl? A Licensed Vet Tech explains normal mouse eating behavior and when to watch for aggression. Get expert insights.
Updated on December 04, 2025
Petco Pet Education Center
Health & Wellbeing
My degu lost teeth after an accident. How can I feed him soft foods?
Your degu had an accident, lost teeth, and can't eat hard food. A Petco Vet Tech offers crucial advice on immediate vet care and how to feed your injured degu.
Updated on December 04, 2025
Petco Pet Education Center
Health & Wellbeing
My pet has a skin issue. Is it mites or ringworm? What's the treatment?
Concerned about Spiky's unknown condition? A certified veterinarian discusses potential mite infestation or ringworm, stressing professional diagnosis and treatment.
Updated on December 04, 2025
image
Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Book Now

Sponsored