the only reason they should be in the same cage is for breeding only(i know all to well because i asked the same question about a month ago when i first joined this site). its ok to take pics of them together briefly if the new ball has been quarentined, otherwise keep them seperate. as far as interaction goes when i had my BP's together they ignored eachother except for the first like... hour, when they were curious why the other was there. and i noticed that the bigger one kept curling around "cuttling" the other on. i later found out that, that was the big one asserting dominance over the smaller one.