how many to add at a time?

[wrslrcichlid]

With the JD I would agree that you shouldn't add more fish. Once you trade/sell him then I would suggest adding more fish.

I had a 55g african cichlid tank with about 30 fish. Granted I was in the process of upgrading to a 125g and the majority of the fish were still juveniles, so I would not suggest that number for the full lifespan of the fish. Depending on species (and assuming you over filter and are willing to keep up with water changes) I would suggest you go for a range of 12-15, maybe 20 if you choose smaller species.

 

[poppalina]

I'm not a fan of over stocking but when it comes to mbuna and tropheus it is almost required. The larger cichlids the reach 8" need their space.

 

[wrslrcichlid]

Also, to answer you original question, I personally like to add all of the fish I want at once. I know that probably goes against popular convention, but I just do lots of water changes to start to allow the BB time to catch up to the bioload. I choose this method because I have found introducing in groups often leads to aggression issues.

This is just my $.02, obviously there are other ways.