is my molly being territorial?

Question
i am a beginner aquariuminer and i bought 3 razboras and 1 molly and they
have been living rather happily in my old 20 gallon tank.  life was good, but
today, i bought another molly and a sweet silver catfish cousin.  i don't think
hello jenny,
i wanna sign up for fish babies, so i made sure to get another boy molly.  i
noted the new molly is definately smaller than the other, and the big boy
chases him around and bumps or nips his belly.  he doesn't seem to do this to
any of the other fish... is he confused and horny, or being mean?  should i be
concerned about the littler one? i certainly don't want him to be pestered to
death.  thanks so much, i really appreciate it.

Answer
Hi Brooke:
The new molly is most likely just a little concerned about her new surroundings, and is very vulnerable. The boy is probably resentful about the newcomer, and will loosen up about it soon. The newcomer will get tougher and know what to expect. Don't worry-it's just a phase. Ask a follow-up if it continues more than a week. It could be more serious than it sounds.
Good luck!
-Jenny