New/old World Cichlid Mixing

[JMatthew]

So, we always talk about not mixing New and Old World Cichilds, but I have never really found out why. I just remember hearing it a million times and then taking it for grant. Last night I picked up a breeding pair of Green Terror from someone who had them in a Mbuna tank and was mentioning to my wife that it was a big 'no-no' and she, of course, asked why - I had no answer. I do understand that Mbuna require a slightly higher pH, but I'm not sure if there is normally a reason beyond this.

Anyway, these Green Terrors look as if they needed to get out of this tank either way as there was obvious fin damage (and even 1 scale damaged on the female) from the Mbuna who out numbered them. They are in a tank all to themsevles now and hopefully they will recoperate quickly.

 

[Davo86]

Apart from the difference in water conditions, dietary needs, habitats, and size,

With mbuna you are required to overstock them in order for the aggression to be spread out and have no (or few) fatalities.
With Central american cichlids however the key is to greatly understock in order to prevent or minimise fatalities.

When the two groups are kept together, at least one group will not be able to thrive

 

[JMatthew]

Sounds fair enough - and that would explain why the Green Terrors were having such a hard time in a tank full or Mbuna.

 

[dthoffsett]

Apart from the difference in water conditions, dietary needs, habitats, and size,

With mbuna you are required to overstock them in order for the aggression to be spread out and have no (or few) fatalities.
With Central american cichlids however the key is to greatly understock in order to prevent or minimise fatalities.

When the two groups are kept together, at least one group will not be able to thrive

Not only that, but as New/Old World never meet in the wild they can't communicate with each other. Anyone who's kept cichlids for awhile will start to recognize their body language, it becomes obvious what is posturing and what is an attack. This inability to communicate will often lead to fatal fights that never would have occured otherwise.

IMO that is the answer to almost all violent deaths in mixed tanks. Most fights among cichlids of same or similar species are a lot of posturing or some missing scales and split fins, but if neither species can read when the other is trying to back down they keep fighting until one of them dies.