I have a 48 gal tank with two small Electric Yellows and 2 OB's (full description below). I want to add some Jewel Cichlids to the tank, but I'm not sure how many to get? How many is best for the Jewel's?
As they come from completely different environments with very different water conditions, I would not mix the two types of cichlids you are talking about. I will leave it to others with more experience with Malawi cichlids to tell you how many more of those it would be OK to add.
In a tank that size, I wouldn't add any more estherae. You could add 2-3 more yellow labs, though, and a trio of synodontis petricola. I wouldn't go beyond that, though...