Well I've had about 7 gold fish living in my pond just fine and peacefully till today, 4-5 of the gold fish were chasing my shubunkin, rolling her on her side and upside down, and really tearing at her her anal and tail fins are really torn up and she is quite worn out, I have her moved into my 30gallon comunity tank for now to recover. Is this mating behavior or what is up?