I have my 3" pair of Sajica's in a 75g with lots of rocks, driftwood and plants (plastic). Want to stay with CA's since my water is on the hard side. Some ideas I had were Nic, JD, Salvini, or GT.
With 3 pair in that size tank, I personally would not add more cichlids.
Maybe some surface dwelling geographically correct live bearers.
At adult size I would have considered my sajica pair alone as topping out the volume of that tank, with some dithers. Notice the comparison to the sugar bowl in the back ground
My male, in the shot below was @ 7" and almost as tall.
And the pair bumped off a slightly smaller size pair when spawning was eminent, in a similar size tank.
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A established breeding pair will make it very hard for any new cichlid to settle into this tank. I'd go with dither fish like duanes recommended.