Update:
Two weeks ago I decided to split my group of 14 into 2 separate groups. After one failed spawning attempt nothing was going on anymore so I made the choise to try and give the dominant male more chanche of a succesful spawn.
I took the dominant male and gave him 2 large gravid females and 1 more submissive male. The others stayed behind to form the second group.
In the second group one of the large, I think also old male, took residence in a cave. Something he hadn't done yet, he alsways sat under a piece of rock or wood. Very busy fanning and seeming to be very happy with the new setup. He has not got eggs (yet) but the fact that he has become the dominant male of this group is incouraging. Females are showing some intrest but patience is the game her, there is a new boss.
In the first group, with the dominant male of the old setup (same male wich gave me my first fry) there has been remarkable succes. After only 2 weeks he's seduced a female last night and is now fanning a new batch of eggs

Not bothered by other males I hope this time he will succeed again in producing some beautiful fry.
Maybe the conclusion is that the size of the breeding group does matter and also the ratio of male and females?? I gave him the best possible chanche with the 2 very gravid females. Not changing anything else in the tank other than separating it into 2 halfs. Feeding and water didn't change either.
Keeping fingers crossed
