Petco Text Logo
Petco Pet Logo

My goldfish has a fuzzy white growth. Is it fungus? How do I treat it?

Updated On September 23rd, 2025

I have two comet goldfish. I realized that one of them was turning a brownish-black color. After a bit of research I realized that the level of ammonia was to blame and so I did a 100 % water change. After the water was clean I saw that my other fish has a white streak that runs across his lower half. From the side it looks flat but from about it looks a bit fuzzy. It might be fungus but I'm not entirely sure. Can you help yo identify what it is and how to get rid of it? Please and Thank You

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

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

1 Answer

Most Helpful Answer

Image profile

Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on August 29th, 2017

If it is fuzzy, it is likely fungal. You can try with a commercial antifungal medication such as API Fungal Cure, methylene blue or Pimafix/Melafix. These can be purchased online or in the aquarium section of most pet stores. Read package directions carefully and remove the carbon insert from the filter before treatment if indicated. Plain aquarium salt (NOT table salt) can be used in conjunction with one of the above treatments to aid healing. Dissolve up to one tablespoon per gallon of water into the tank. Fungal infections can take up to two weeks to resolve with treatment. Maintain proper water parameters (0 ppm ammonia/nitrites, 40ppm or less nitrates and temp of 65 F to 72 F). If possible, remove the affected fish yo a hospital tank during treatment.

Vote icon

1Pet Parents found this answer helpful

image
Have A Vet Question?

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

Sponsored