I have an adult pair which have yet to breed. The male fish has started to harass the female. The result of this is that the female now has a badly torn tail. I have also seen this in a blue diamond pair. What is the cause of this?
This is quite a headache problem.
It is quite common things that used to happen.
It is sometime male fights the female; or female fights the male.
Somebody is stubborn; do not want to start work, will get bitten.
Separate them temporary or pair up with other fish if possible.