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My betta has red fin tips and corydoras have red spots. What's wrong?

Updated on September 23rd, 2025

Pet's info: Fish | Unknown - Fish

My betta has red tips on his tail and my cat fish Cory has red spots as well

2 Answers

Most Helpful Answer

Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on February 27th, 2018

This could be bacterial infection. Most minor infection can be managed or resolved by providing pristine water conditions and a tiny bit of plain aquarium salt (NOT table or Epsom salt). Perform daily partial water changes, about 30%, using aged or conditioned water that is temperature matched to prevent further stress or shock. Dissolve about 1/2 teaspoon of plain aquarium salt per gallon of water into the tank. Treat for 10-14 days then reassess their condition. If necessary a broad spectrum antibiotic can be found in the aquarium section of the local Petco. Follow label directions carefully.
As an aside, Bettas do best between 78F and 80F. Cory cats prefer cooler temps, between 60F and 75F. They do not do well at temps that Bettas are kept in, eventually they will become stressed which can lead to infection. Consider separating one or the other into a tank with the appropriate water parameters.

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Angel Alvarado, LVT
Licensed Veterinary Technician
Published on March 3rd, 2019
Poor water quality can cause stress which can lead to infection. Check the water chemistry and quality first. You can use a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for 0 ppm ammonia and nitrites with nitrates at 20ppm or less. Perform a partial water change (no more than 30% total volume at once) to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Bettas are tropical fish and do best between 78 F and 80 F. Add a teaspoon of plain aquarium salt (NOT table or Epsom salt) per gallon of water to the tank. Dissolve it first in a cup or two of tank water. The salt will reduce stress, improve gill function, treat minor infection and aid in recovery. Treat for 14 days then reassess fin condition. Perform partial water changes afterwards to decrease salinity.
At the same time, withhold food for 2-3 days. Resume feeding bits of cooked, shelled green peas. This may help with constipation which can affect the swim bladder. Feed peas until swimming and defecation are normal. You can soak the bits in some garlic juice to stimulate the appetite and provide an immune system boost.
If there is no change, consider a broad spectrum antibiotic or "all in one" treatment, such as Lifeguard (by Tetra). Find either in the aquarium section at the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.
1Pet Parents found this answer helpful

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