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 fourfemales, 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…