Suddenly Aggressive!

[Starfirefly26]

Of my current stock, the group that was here from the start consits of a female Balloon Molly, a Male Sunrise Guppy, and a Female Red Wag.

Now, the Red Wag has always been passive, so lets skip her.

For a while it seemed as though the Guppy would nip at the Molly, her sides or something. Nothing big came of this until today (my tank is about...3 weeks to a month old).
Today I watched as my Balloon Molly raced for my Guppy until he darted off. If he would get close to her, she'd go after him.

Now, I've got the guppy in a breeding trap (small size, he's got a bit of room), because I don't know what's going on. Is this normal? I'm afraid she's going to rip up his tail, and considering I'm giving him to my sister for a classroom tank, it'd be nice to give her a happy and healthy fish.
The changes have been a live plant, two fakes, a new decoration, air stone, and some rearrangement. I just noticed this agressive behavior when I slipped in a small bit of frozen brine shrimp and some fish flakes (since the Juvies hogged all the brine shrimp...)

I'm a tad panicky, but not feeling as bad since one of them is conatined

Any ideas on what's wrong?

 

[blitztidus]

They may have been fighting over food or she was just getting really bugged. Just asking, but how long until he goes to your sister

 

[Starfirefly26]

When her tank gets set up. She's been busy and whatnot, so she hasn't been able to get the supplies from the school she works at(they're willing to supply her the filters and whatnot).

I'll be sad to see him go, but it will be much happier for my tank if the females aren't putting out babies every month.
(I was also ill-advised to an algae eater...with salt in the tank...and I had 3 neons, 2 of which died. we're buying two and giving her those three as well)

EDIT: I let him back in...but looked today and found out he's got a small rip in his tail. I seperated him to avoid getting his tail torn to bits.