Hi Neil
First I would ask how big are your peppy's now and what is the sex ratio. I find my breeding males tend to be very teritorial and although they havn't harmed each other I have stuck to the safer side (seperation). My personal opinion is a 2 foot cube is to small for 6 adult pep's. I would seperate into trio's if you have the correct ratio. 1M-2F
Cheers Tropo