Swordtails attacking our other fish

Question
Hi, we have a 3ft by 1 and 1/2 foot tank with 3 female swordtails, 1 male swordtail, 1 algae eater and 3 different types of goldfish. In the last couple of days our swordtail fish have been attacking our goldfish. Our goldfish are alot bigger than our swordtails. 1 of the female swordtails are pregnant and has some fry not to long ago. PH level is good temp is good, i cleaned the water not on the weekend (25%) i do that every fortnight. Can you please tell me why they are attacking our goldfish?

Answer
Hi Sarah,
  Many fish are territorial and swordtails are no exception.  

I stronlgy recommend that people put a lot of "structure" (rock, wood, plants, etc) in a tank to break up the space and to provide lots of hiding places for a fish if it is being attacked.  

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>