Balance of Imbalance: Case Study in Reverse Trio Dynamics

 

Mbuna, as any experienced African cichlid keeper should know, are generally best kept in a ratio of multiple females per male. Most mbuna, however, are purchased as unsexed juveniles. If you want to be sure to end up with just one male and three or four females, you would need to purchase a larger number of fish and return any excess males as they reveal themselves. In practice many hobbyists simply purchase four fish and hope they’ll end up with a 1m:3f ratio; however, there is statistically only about a one in four chance this will be the case.

 

A few years ago I committed the aforementioned act of wishful thinking and purchased four young Melanochromis cyaneorhabdos. Sure enough, they did not turn out to be 1m:3f, but rather 2m:2f. Both females were under constant pressure to breed from the males, and within a year one of them wasted away. I never recuperated any fry from them during that period, as the females always seemed to be under such pressure from the males that they would swallow their eggs.

 

Given that state of affairs, when I was down to one female I didn’t have high hopes for the remaining one to survive let alone breed. Well, survive she did, for the past two plus years. What happened was this: one of the two males clearly emerged as the dominant one. His time was divided between pressuring the female to breed and keeping the subdominant male in his place. Therefore going from 2m:2f to 2m:1f, instead of doubling the pressure to breed on the remaining female, actually reduced it.

 

Breeding was still not great during this period as the female would still tend to swallow her eggs. On one occasion I did see two fry among the rocks; however, the adult fish in the tank got to them before I could. Only just recently did I notice the female holding at a moment when I could afford the time to remove all the rocks and catch her (she’s a wily one, which must have helped her survive the past few years). She is now resting peacefully in the 10 gallon maternity ward, biding her time to release the brood.

 

Meanwhile, back in the main tank, the subdominant male is suffering the full attention of the dominant male, and is looking the worse for it. You would think that the absence of females to fight over would have lessened the aggression; however, M. cyaneorhabdos males are known for their intolerance of each other. “No girls to fight over right now, but I should get rid of this other guy anyways in case any come along,” seems to be the approach they take. Hopefully the subdominant male hangs in there long enough for me to return the female to the tank and restore the reverse trio.

 

This sort of ‘success’ story should be served with a few caveats. The 2m:1f ratio in this instance has been a delicate balance. The aquarium in question is a moderately rocked 6-footer. The reverse trio may not have lasted in a 4’ tank or may have required it to be very heavily rocked for it to work. Also, reverse ratios that are more severely skewed, for instance 4m:1f, may not work simply because at some point there would be too many competitors for the dominant male to keep down at once. An outnumbered female(s) would suffer for it. For some species there may be no such thing as a successful reverse ratio at all (can anyone say ‘auratus’?).

 

It is not the purpose of this article to recommend reverse ratios with mbuna – far from it! In hindsight I can explain why it worked in this particular situation. I have also heard of the odd similar experience from other hobbyists, but this sort of equilibrium is too fragile to be reliable. It is, in a sense, a ‘balance of imbalance.” Interesting to observe when it happens, but not something to aim for…

IN PROGRESS -TCHILL-Final Edit-2/24/09