I have a very healthy betta in a cycled 10 gallon tank. All levels read well (ammonia 0, Nitrite 0, Nitrate 10 ph around 7) He has been living there for about 2 to 3 weeks and has been fine.
Yesterday my resident called me and told me that she noticed his fins got very short. He usually likes to hang around the part of the filter that sticks down into the water. Could he have possibly cut his fins on that? Or is he becoming a tail biter?
Here are some pictures:
Here are the before pictures that I took last year around November: