The same applies here, while by no means will you find all the killies here near impossible to keep or breed, these species tend to give even the most advanced hobbyist fits and while maintaining them is not particularly difficult in most cases, breeding them, at all, or in numbers more than a handfull represents rather a challenge, to say the least.
In some cases, this may be a function of time; Psudoepiplatys annulatus was once regarded by very accomplished hobbyists as a very difficult species, yet there are people today who breed them by the hundreds.