Re: Goldfish attacking each other...mating; sick?
#3
It sounds like mating attempts to me
Water changes often trigger a bit of loving as the slight reduction in temperature sets them off
When mine are in the mood for love the male swims against the female, nips her bum, shoves her around, sits on her head etc. etc!
It can be exhausting for the female, expecially if she has two of them after her so keep an eye on her and consider removing one of them for a while if it gets too much
Keep an eye on her for injuries especially if they are shoving her against stones.
Females usually have an 'outie' vent and males have an 'innie' but it's not always that easy to tell especially if the fish is round bodied. The fact that the suspected female is wider is an indicator that she is indeed a female.
HTH - poor little girl!
It's Not Just A Fish