what makes haps/peacocks grow longer fins?

[Hybridfish7]

I see it on some really nice specimens of various aulonocara sp. and a variety of haps. Is there anything specific that induces the growth of their finnage?
examples of what I mean:
b.atritaeniatus

c.azureus

a.walteri

 

[ryang85]

I personally find the longest fins on the most domant and older males where there are very few other fish in the tank to bite at fins. It also requires prestine water parameters to prevent any type of fin rot. I'm sure genetics also play into it.

 

[DJRansome]

DNA makes the fish capable of growing the length. But show fish with long fins are probably kept isolated for long periods before the show to avoid damage and maximize length. Like a year possibly.

 

[neutrino]

Age, good food, clean water, fins not being nipped, not too much chasing. Mostly simple stuff. More dominant fish may tend to have showier fins, sometimes it's just the individual fish and some species typically have showy fins, like the A. jacobfriebergi in the bottom photo, and some individuals will flare/display their fins more than others.