I had many breeding setups with different species in 29's and all of them were happy and breeding(I also put in extra hiding spaces).The 29 gallon is 30''x12'' and that makes it have the footprint of 360 square inches. Half of a 75 gallon is 24''x18'' which has a footprint of 432 square inches. So if I were to breed the two in this tank it would be better than having one group in a 29.
Also I do understand what you are saying but my hongi is about 4'' and has stopped growing a long time ago, and the bicolor is about 3''. When the bicolor gets to 5'' I'm probably going to work something else out.
That much I agree with. lol But honestly most cichlids will breed in a bucket if given half the chance. Breeding is not exactly a sign of "happiness", or equal to the fish living in ideal conditions. Not the way that I bred African cichlids, but to each their own.
Just to add, for species that can fit through egg crate I have used sheets of plexi-glass that I have drilled out. Both work equally well, but egg crate allows better flow between the sections.
I've tried to breed placidochromis electra "black face lawani" is a 36" 40 gallon. This is a really rare collection point for electra, so they weren't easy to find. The male decided to kill all 4 females, even though electra are considered peaceful. It's been probably 6 years and I've yet to find these again. I would definitely aim for a bigger tank if I wanted to try breeding again, even peaceful species.
Agree, I always use egg crate (AKA light diffuser in some hardware stores), it allows for almost completely unrestricted water flow for filtration, yet keeps adult cichlids apart. When I cut it to fit, I use the trimmings to brace horizontal pieces with vertical ones, below, and on the sides, using zip ties to secure them together
Also like to cut a notch to securely fit the divider into the aquariums frame.
I sometimes place rocks on horizontal pieces to add more security.