[Kabernick30]

I have a 26 Gallon aquarium with compatible fish and regulated water parameters, however overnight one of Cory catfish developed clear bubble like things where its dorsal fin meets its back as well as in between its back fins by its tail.

Ive attached a picture and I really need some help to know how to treat this

 

[dancelady]

Could you tell us more details, please

I see the picture, but more details are needed. Are the "bubbles" still there, or have they disappeared? Did you notice any other symptoms such as peculiar movement, other things on their sides, other Corys hanging around (like to mate), little eggs on the glass, or other such items? I need more info to help, and more detail on your water conditions -- what type of Corys are they, which parameters are most important for that particular Cory? They are not the standard Bronze, Albino, or Panda, so be more specific.

 

[Sylverclaws]

I wonder if it could be gas bubble disease. Happens when you add colder water to the tank(I think it can happen with warmer water added too). I dunno if there are other causes for it as well, but there probably is. I had seen it in a post on a cardinal tetra that had this, and the owner had added chilled water to the tank. It only hit one.
And if I recall correctly, you need to oxygenate the tank really well for treatment. I dunno if it happens to cories or if it's tetra specific, but do look into that, it's the only thing I can think of, but I can't see it well enough.