previously mated platys fighting
I have a pair of platys which have been utterly inseparable for the last year or so -- they are the only platys in the tank and have successfully bred a few times.
suddenly, one of them is hiding all the time and the other one seems to be bullying it -- chasing it and trying to nip at it.
any ideas what could have caused this?
they are in a 60L tank with some danios and a few minnows.