How to Treat a Guppy with Fin Rot

Updated April 17, 2017

Guppies are common freshwater fish and add a colourful display to any aquarium. Occasionally, guppies' fins are damaged by sharp objects in their tank or by other fish. These fish become weakened and due to poor water conditions, a disease such a fin rot sets in. Fin rot is a bacterial disease in which the fin first experiences a milky white appearance, followed by actually fin disintegration and shredding. By following a simple procedure, you can treat your guppy for fin rot.

Inspect guppies for any fish with a visible fin deterioration. Remove these fish from the aquarium using a fish net, and put them in a separate holding tank with clean and well-aerated water. Also, remove healthy guppies from the aquarium and place them in another holding tank separate from the infected guppies.

Turn off all aquarium equipment, and wait approximately 5 minutes for the equipment to cool before removing water from the tank. Wash and clean the tank using aquarium-approved cleaning products from a pet store. Make sure to clean the gravel, filter system and other decorative items in the tank.

Return the gravel, filter system and decorative item to the aquarium. Next, replace the water in the tank using clean water at room temperature. Wait approximately 5 minute to plug in the aquarium equipment. Place healthy guppies from the holding tank into the aquarium.

Treat infected guppies held in the holding tank with an antibacterial medicine according to package directions. There are several products such as Melafix that treat antibacterial infections. If the fin rot is at the progressive stage, you can treat it with an antibiotic such as Tetracycline, according to package directions. It will take several days for the fin rot to clear up.

Return the guppies to the aquarium after all signs of fin rot have disappeared.


Keeping the aquarium clean and water conditions consistent will help prevent fin rot.


Do not clean aquarium with soap or household cleaning products.

Things You'll Need

  • Fish net
  • 2 holding tanks
  • Anti-bacterial medicine
  • Antibiotic medicine
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About the Author

Jeannine Lowe is a business technology teacher at McKenzie High School in Tennessee. She has been writing on business and marketing topics since 2007. Lowe obtained her Master of Science in education through Walden University, specializing in integrating technology into the classroom.