Chromis need to be fed as frequently as anthias, if you want to keep the entire school, rather than they kill each other over food, as the weakest are forced out.
Dart or fire fish gobies, will try to pair out.
I've bred banggai cardinals in the past, and only females, juvenile males and mouth brooding males will school. Individual dominant males will hold 3D territories in the water column and "fight" off other dominant males.
In my 75 gallon, there is enough space for 2 territories. (left and right side) In the beginning, there only enough space for the dominant male, and the school is forced to the other side, but shortly afterwards, the next sub dominant male will take the other space and the rest of the school wont fit and have to be removed.
I've visited the public aquarium (Loveland) at Salt Lake City, and they have a large system, must be over 5' by 10', where the 100+ banggai cardinals where shoolling, and the males held territories about 2-3 feet apart from each other. The males would not allow any other cardinal in their breeding territories, except for a ripe female. There were multiple males holding within the school. The school was hovering over an open sandy area, where there was no dominant male.
As for schooling, I have set up a gyre in my system that spins the water lie a whirl pool, around a center reef. The water will spin clockwise around the reef, and the rock work is away from the back wall. Within the grye, most of my fish appear to "school" by swimming against the current, along the front glass. I guess they could swim against the back glass as well, but since there's nothing to see there, they prefer to be "schooling" on the outside and into my room. If the current is too slow, there is no schooling behavior. If the water is moving fast, they are forced to school, just to stay in position.
