What is wrong with my fish

Lunyone · Jun 28, 2026

does anyone know what the lump is on my white fin tetra?

GaryE · Jun 28, 2026

It's a grainy photo, but it looks like Lymphocystitis, a viral infection that often hits highly stressed fish. Check images of the disease online to confirm.
If I'm right, increase your weekly water changes and run a clean tank. I realize it may have come with a new fish from a store, so no blame. But regular weekly water changes of 30% or more will let the virus run its course and hopefully vanish.

There are no treatment for this virus except time. It will spread to other fish if that one dies and they scavenge it. With with a reduction in stress from poor water quality it should run its course and vanish.

Stress. What else is in there with it, and how many white fins do you have?

Lunyone · Jun 28, 2026

GaryE said:
It's a grainy photo, but it looks like Lymphocystitis, a viral infection that often hits highly stressed fish. Check images of the disease online to confirm.
If I'm right, increase your weekly water changes and run a clean tank. I realize it may have come with a new fish from a store, so no blame. But regular weekly water changes of 30% or more will let the virus run its course and hopefully vanish.

There are no treatment for this virus except time. It will spread to other fish if that one dies and they scavenge it. With with a reduction in stress from poor water quality it should run its course and vanish.

Stress. What else is in there with it, and how many white fins do you have?

The water is clean and I have 2 other white fin tetra black fin tetra Buenos Aries tetra giant danios albino bristle nose placostomas another pleco can't remember what kind. Black neon tetra to name a few. I have had the white fin and black fin tetras a few years. The one with the bump acts like nothing is wrong.

Lunyone · Jun 28, 2026

Lunyone said:
The water is clean and I have 2 other white fin tetra black fin tetra Buenos Aries tetra giant danios albino bristle nose placostomas another pleco can't remember what kind. Black neon tetra to name a few. I have had the white fin and black fin tetras a few years. The one with the bump acts like nothing is wrong.

I must add the lump is under the skin/scales.

GaryE · Jun 28, 2026

That's consistent with lymphocystitis. It's ugly but the fish isn't usually bothered by it. Patience is the cure, patience and regular partial water changes.