Do fish get cataracts? im not sure what this is, hes a relatively new fish, ive had him for about a week, in a ten gallon heated, filtered, conditioned tank. it dosent seem to be affecting his eyesight or anything, because he still gobbles his food up and swims up to the glass when i come into the room. also, its only on his right eye.
Could be ammonia burn from however he was kept before you got him .. hopefully not cloudy eye. So make sure his water's spotless, like ammonia free totally. If it gets bigger or 'whiter', hospital tank and dose him with AQ salt, 1 tsp per gallon for a week. If that doesn't work, or it gets worse still, I'd say it's bacterial.. but I'd just see how a few more days of really clean water does for him first, then the salt if necessary.
Its not an ammonia burn. The person who she got them from does every other day 100% water changes on all of there tanks.
He doesn't seem to have cataracts, you can't see that scaling over the eye and it doesn't look cloudy, here's an example of a blind Betta
Could be trauma, I had a fish with an eye like that, and im really not sure what caused it but she was blind on one side. Right now I would focus on seeing if its affecting his vision, and if so, trying to acomodate him. If his vision is good in the other eye, you may not need to worry, ut if it is not, I would suggest softer plants and decor, and mybe linign the edges with plants and soft stuff so he doesnt run into the glass.
Had a betta with exactly the same problem when I was a kid. I actually looked in the yellow pages, called a vet and asked about cataracts in fish.... The vet had no clue (and likely thought I was crazy).
That was about 20 years ago.
I've learned a lot since then about bettas but one thing I learned as a kid still holds true. Clean water. I agree with the above posters- change the water. Even if the owner did frequent changes, things could have changed during shipping. And whether it was trauma, poor water quality, whatever, clean water will help.
My betta's eye cleared up after 2 water changes in 2 days when I was a kid, though at the time I did not understand anything about water quality.