Why did my Cory die?

[Samuel Tabares A]

Hello 

I have a community tank with seven corydoras, that I ve had for about 3 months with no issue. I have not added any new animals to the tank in about 1.5 months. 

Today at lunch, I saw a cory cat swimming in the surface, I isolated it in a 5gallon bucket with some water from the same tank and an air stone but it died a few minutes later.

It has something on its side.

Everyone in the tank is doing great.

Tank mates are tetras serpae, ruby tetras, neon tetras, cherry shrimp and a blue phantom pleco. 34 gallons 

Temperature constant 24 C ( no heater I live in the tropics )

Ph 7

Ammonia 0 

Planted tank 

[Colu]

It look like it could be red blotch disease it a common disease of  corydoras   I would treat with maracyn2 and aquarium salt 1table spoon for 3gallons  your Tetras won't get red blotch disease they should be fine

Edited June 10 by Colu

[Samuel Tabares A]

Thanks !