twitching and mating behaviors

[OceanLover]

In my sister's tank the dalmation molly has began showing 'mating behaviors' towards her fruit tetra. The fruit tetra has apparently began twitching and it seems to only grow worse. She also has started hiding behind the plants. Is the twitching related to his behavior?? I have no idea how to approach this! Please help?

 

[OceanLover]

The dalmation molly has died, we don't know why (I am not there to watch over her shoulder), but the fruit tetra still has a twitch. *shrug*

 

[missileman]

What are the water parameters?