Hi! Welcome to fishlore!
I've never kept keyhole cichlids either, but as a suggestion for compatible schooling fish, I would go with the rasboras, or tetras. Danios and barbs are also very good schooling fish, but they are very active, and hyper, so I don't know how your cichlids would react to them.
As for the tetras and rasboras, I suggest you get a peaceful schooling fish, such as harlequin rasboras, and maybe neon tetras. I have neon tetras myself, and they are very placid, and don't bother the other fish.
Hope I helped!
~ Ali
