Need advice on Red Eyed Tetra Gills
I acquired 3 Red Eyed Tetras about 7 weeks ago. Long story short, they were not returnable and were received in pretty bad condition. They were all 3 covered in ammonia burn, and 2 of the 3 had what looks like severely inflamed gills. Two of them have deformed mouths. One unable to close, the other bent to the side a bit as well as a deformed spine. They have gone through a round of General cure, and Furan-2 and that cleared the redness on their bodies, but there has been no change to their gills. The female looked normal aside from ammonia burn, and has not gotten any worse either. The 3 of them all have healthy appetites and exhibit normal healthy tetra behavior. I have not witnessed any flashing or stress from them despite their afflictions.
I originally suspected gill flukes just based on the condition of their gills, but I have never had experience with flukes so I was looking for some advice. Is it possible that they were injured or just born this way, or could these fish be infected with gill flukes for 7+ weeks without getting any worse?
They are in a quarantine tank. It is about 9 gallons with 25-30% water changes weekly. Ammonia and nitrite is 0ppm, nitrate 10ppm. I will attach some of the photos that I have of them and take better ones when I get home.