my thoughts are it is good in some instances, I have down sized ready for my house sale,
so currently have one breeding pair of ancistrus in my main tank, whilst at the same time
there are 4 male and 4 female peppermints in there also.
Do not hold your hopes up for them breeding as often as keeping more males to female ratio can mean they
do not pair off as good and breed as much.
It can also mean that some fish get aggressive, or territorial. Just keep your eye on them and if any fights break out then get ready to part them.
My peppermints have been ok for the 3 months they have been together, though some other fish keepers are not as lucky.
I tend to play on the side of caution and whenever I put more males in the tank I will always increase my inner surface capacity
with extra caves, coconut shells, plumbing pipes, rocks, shells, plants, plant pots and ornaments.
This helps to give the cat fish more area on the bottom to hide, as well as providing more surface area for algae to grow,
plus more territories for them to acquire.
Each to their own really.... I only have had problems once and that was with two female's lol....
They were fighting over the male...lol...
Kind of funny really as I was not expecting that at all..
We all learn, I tend to write things down so I can look back on what as worked and may not.
Alternatively if not I tend to let others know on here, that way by sharing we get more constructive, and reflective input.
No doubt others will have varying views, that is why this site is always so good.... you always get good mixed advice
Good luck and keep us posted...