This is a discussion on Adding dwarf cichlids within the Cichlids forums, part of the Freshwater and Tropical Fish category; -->
I'm planning to add a pair of apistos to my GBR tank. I have a 24gallon tank measures 25" long, 16"high, and ...
I would not. A 24g tank can house one pair/harem of a (small) cichlid, but not more than one species. I have had two species of Apistogramma in my 4-foot 90g and 70g tanks, and they did not get along.
It is during spawning/care of the eggs and fry that the trouble occurs. Females are very protective and will easily kill other females, and the male if he is good at defending his territory will as well. And cichlids will continue spawning regularly, so this is an on-going issue.
Tanks under 4 feet should not have more than one species of cichlid.
Even in a 90G tank? i suppose you have more than a pair?
Is it ok to add another GBR pair though?
If there is a lot of wood and plants to break up the line of sight and the substrate, then two pairs should manage. Remember that Mikrogeophagus ramirezi form bonded pairs, which means that the fish select their own mates. Adding any male and any female to a tank with an existing pair may be tragic.