It is an interesting question. I had 6 young adults in a 225, I got unlucky. they formed three pair. Two of the pair sort of got along. The third pair decided they wanted nothing to do with the others (sort of a random decision made in the cover of darkness one night). I had to remove the other 4 or they would have died as a result of injuries.
Try to avoid pairs and you have a better chance of increasing specimen count. Then you just get into conspefic conflict. Cichlids can be a challenge.
Or, you might just end up with 3-5 that tolerate each other and never exhibit problems.
Nothing black and white, No rule, just lots of shades of grey.