I'm not sure what you mean. You can use CA cichlids as dithers. Severums and convicts make great dithers. A pleco is good for the bottom and loaches get along well with CA cichlids (my Midas, Severums, and Green Terror totally ignore them). If worried about size, I think you'll find loaches grow rather quickly on cichlid food.
You can use dang near anything you want as long as it won't fit in the mouth of others, and the primary fish aren't overly aggressive. Dainty freshwater fish usually won't fare well.