revolt in severum tank: which ones should I remove?

I got a nice couple of severums with fry and 3 others, of which one
claimed her (I believe it's a she) territory. everything was fine until
today: the solitary female (a big one compared to the rest) expanded her
territory at the cost of the couple's, the male sent his wife off to fight
the threat, but she seemed not fit enough to handle it. now I've got one
parent guarding the fry and his significant other chased by both him
and the rebellious female.

I already planned to take out the remaining three as soon as the couple
spawned for the second time, but now I start to doubt. they had quarrels
before, I guess I have to take out everything out but the couple... will
removing the fry improve peace as well? the fry's mother is hurt quite
badly and I think that it is wise to act quickly.