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Why is my fish's tail disappearing and tank getting brown algae?

Updated on September 23rd, 2025

Pet's info: Fish | Unknown - Fish | Male

My fish has been slowly losing pieces of his tail, and a weird brown stuff is growing on the tank. I clean it every week, but it won't go away and his tail won't grow back. What do I do?

1 Answer

Most Helpful Answer

Angel Alvarado, LVT

Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on December 10th, 2016

It is likely fin rot which is caused by bacterial overgrowth. It may respond to treatment with simple aquarium salt. Place Alpha in a smaller tank, half gallon to one gallon, for easier treatment. Use 1-1.5 teaspoons per gallon. Perform a 100% water change each day and using a fresh water/salt solution. Do this for a maximum of 10 consecutive days. Strive for a water temp between 76 F and 78 F. This will inhibit bacterial growth. Turn off any tank light to further inhibit bacterial growth. Turn off the filter as the current may slow fin regrowth and the filter media may remove enough salt to affect treatment.
This treatment should clear most cases of fin rot.
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